UPDATE: As many as 20 Britons caught up in Algerian hostage crisis have returned to UK, with a further four expected home by lunchtime, Sky News has reported. The Foreign Secretary is expected to make a statement later on Sunday.

Five British nationals and a UK resident are believed dead or missing as the Algeria hostage crisis ended in a bloody and violent climax.

Foreign Secretary William Hague announced the latest casualties after Algerian special forces mounted a "final assault" on the remaining Islamist militants still holding out at the remote BP gas plant at In Amenas.

"On the basis of the information that we have this evening, we believe that there are five British nationals or one British resident who are either deceased or unaccounted for, in addition to the one fatality that we had already confirmed," he said.

"We are working hard to get definitive information about each individual. We are in touch with all of the families concerned."

locator map algeria

The Algerian Interior Ministry said a total of 23 hostages and 32 terrorists had been killed, and 107 foreign workers and 685 local workers had been released.

In a statement on Saturday night the ministry said troops had recovered six machine guns, 21 rifles, two shotguns, two 60mm mortars with shells, six 60mm missiles with launchers, two rocket-propelled grenades with eight rockets and 10 grenades in explosive belts.

Earlier, David Cameron said that he had spoken to Algerian prime minister Abdelmalek Sellal, who confirmed that the four-day hostage crisis was "effectively ended".

"I know that the whole country shares my sympathy and concern for everyone who has been caught up in this incident, and for their friends and families," the Prime Minister said in a statement.

"It is our priority now to get people home as quickly as possible and to look after the survivors. Many are already home or on their way back.

"Let me be clear. There is no justification for taking innocent life in this way.

"Our determination is stronger than ever to work with allies right around the world to root out and defeat this terrorist scourge and those who encourage it."

Seven hostages and 11 of the Islamist militants holding them were reported to have died in the final shoot-out in the vast desert complex close to the Libyan border.

The Algerian state news agency, APS, quoted an Algerian security source as saying that the hostages who died were killed by their captor.

The Algerian authorities were tonight removing explosives left by the militants who booby-trapped the plant before the final battle.

mokhtar belmokhtar

The kidnappers are linked to a terrorist splinter group led by veteran jihadist Mokhtar Belmokhtar

Mr Hague, speaking after chairing the second meeting of the day of the Government's Cobra emergencies committee, refused to be drawn into criticising the Algerian rescue operation, despite the death toll.

"I don't want to at this stage enter into criticism or judgment because there will be a lot to be learned yet about this operation," he said.

"Our focus is very much on getting British nationals who have survived this ordeal and away from that area."

Defence Secretary Philip Hammond said: "The loss of life as a result of these attacks is appalling and unacceptable. We must be clear that it is the terrorists who bear sole responsibility for it."

The kidnappers, part of the Masked Brigade - a terrorist splinter group led by the veteran jihadist, Mokhtar Belmokhtar, which broke away from al Qaida in the Islamic Maghreb - initially claimed the attack was in retaliation for the French military intervention in neighbouring Mali.

It was subsequently reported that they were demanding the release of two terrorists held in the US, including 1993 World Trade Centre bombing mastermind Omar Abdel Rahman, in return for the release of two US captives.

The plant at In Amenas is jointly operated by BP, Norwegian company Statoil and Algerian state oil company Sonatrach.

Meanwhile, BP chief executive Bob Dudley said the company was "unable to confirm the location or situation" of four employees at In Amenas and had "grave fears" that they are likely to have suffered fatalities.

One Algerian worker, who gave his name only as Chabane, described how from his hiding place he heard the militants speaking among themselves with Libyan, Egyptian and Tunisian accents. At one point, he said, they caught a Briton.

"They threatened him until he called out in English to his friends, telling them 'Come out, come out. They're not going to kill you. They're looking for the Americans'," he said.
"A few minutes later they blew him away."

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  • An unidentified rescued hostage speaks to the media in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013. Algeria’s state news service says nearly 100 out of 132 foreign hostages have been freed from a gas plant where Islamist militants had held them captive for three days. The APS news agency report was an unexpected indication of both more hostages than had previously been reported and a potentially breakthrough development in what has been a bloody siege. (AP Photo/Canal Algerie via Assiaciated Press TV) ** TV OUT ALGERIA OUT **

  • Unidentified rescued hostages pose for the media in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013. Algeria’s state news service says nearly 100 out of 132 foreign hostages have been freed from a gas plant where Islamist militants had held them captive for three days. The APS news agency report was an unexpected indication of both more hostages than had previously been reported and a potentially breakthrough development in what has been a bloody siege. (AP Photo/Canal Algerie via Associated Press TV) ** TV OUT ALGERIA OUT **

  • Algerian special police unit officers secure the hospital in Ain Amenas, Algeria, Friday, Jan. 18, 2013, two days after the start of the terrorist attack at a gas plant. The hostage crisis in the remote desert of Algeria is not over, Britain said Friday, after an Algerian raid on the gas plant to wipe out Islamist militants and free their captives from at least 10 countries unleashed bloody chaos. (AP Photo/Anis Belghoul)

  • An unidentified rescued hostage receives treatment in a hospital in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013. Algeria’s state news service says nearly 100 out of 132 foreign hostages have been freed from a gas plant where Islamist militants had held them captive for three days. The APS news agency report was an unexpected indication of both more hostages than had previously been reported and a potentially breakthrough development in what has been a bloody siege. (AP Photo/Canal Algerie via Associated Press TV) ** TV OUT ALGERIA OUT **

  • An unidentified rescued hostage speaks to the media in a hospital in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013. Algeria’s state news service says nearly 100 out of 132 foreign hostages have been freed from a gas plant where Islamist militants had held them captive for three days. The APS news agency report was an unexpected indication of both more hostages than had previously been reported and a potentially breakthrough development in what has been a bloody siege. (AP Photo/Canal Algerie via Associated Press TV) ** TV OUT ALGERIA OUT **

  • This image from video provided by the SITE Intel Group made available Thursday Jan. 17, 2013, purports to show militant militia leader Moktar Belmoktar. Algerian officials scrambled Thursday Jan. 17, 2013 for a way to end an armed standoff deep in the Sahara desert with Islamic militants who have taken dozens of foreigners hostage, turning to tribal Algerian Tuareg leaders for talks and contemplating an international force. The group claiming responsibility — called Katibat Moulathamine or the Masked Brigade — says it has captured 41 foreigners, including seven Americans, in the surprise attack Wednesday on the Ain Amenas gas plant. Algerian Interior Minister Daho Ould Kabila said the roughly 20 well armed gunmen were from Algeria itself, operating under orders from Moktar Belmoktar, al-Qaida's strongman in the Sahara. (AP Photo/SITE Intel Group) THE ASSOCIATED PRESS HAS NO WAY OF INDEPENDENTLY VERIFYING THE CONTENT, LOCATION OR DATE OF THIS PICTURE. MANDATORY CREDIT: SITE Intel Group

  • This April 19, 2005 photo released by Statoil via NTB scanpix, shows the Ain Amenas gas field in Algeria, where Islamist militants raided and took hostages Wednesday Jan. 16, 2013. As Algerian army helicopters clattered overhead deep in the Sahara desert, Islamist militants hunkered down for the night in the natural gas complex they had assaulted Wednesday morning, killing two people and taking dozens of foreigners hostage in what could be the first spillover from France's intervention in Mali. (AP Photo/Kjetil Alsvik, Statoil via NTB scanpix) NORWAY OUT

  • This April 19, 2005 photo released by Statoil via NTB scanpix, shows the Ain Amenas gas field in Algeria, where Islamist militants raided and took hostages Wednesday Jan. 16, 2013. As Algerian army helicopters clattered overhead deep in the Sahara desert, Islamist militants hunkered down for the night in the natural gas complex they had assaulted Wednesday morning, killing two people and taking dozens of foreigners hostage in what could be the first spillover from France's intervention in Mali. (AP Photo/Kjetil Alsvik, Statoil via NTB scanpix) NORWAY OUT

  • JGC Corporation, or Nikki Manager of public relations Takeshi Endo, foreground, answers reporters' questions following Wednesday's attack at a natural gas complex in Algeria which involves the company's workers, at its headquarters in Yokohama, near Tokyo Thursday, Jan. 17, 2013. A militant group that claimed responsibility said 41 foreigners were being held after the assault on one of oil-rich Algeria's energy facilities. Two foreigners were killed. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO LICENSING IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

  • Helge Lund

    Statoil Chief Executive Helge Lund answers questions about the situation in the gas field, jointly operated by BP, the Norwegian energy company Statoil and the Algerian state oil company Sonatrachfield along with Japanese company JGC Corp., in Ain Amenas in Algeria during a press briefing in Stavanger, Norway, Thursday, Jan. 17, 2013. In a desert standoff deep in the Sahara, the Algerian army ringed the natural gas complex where Islamist militants hunkered down with dozens of hostages Wednesday night after a rare attack that appeared to be the first violent shock wave from the French intervention in Mali. (AP Photo/NTB Scanpix, Kent Skibstad) NORWAY OUT

  • Helge Lund

    Statoil Chief Executive Helge Lund answers questions about the situation in the gas field, jointly operated by BP, the Norwegian energy company Statoil and the Algerian state oil company Sonatrachfield along with Japanese company JGC Corp., in Ain Amenas in Algeria during a press briefing in Stavanger, Norway, Thursday, Jan. 17, 2013. In a desert standoff deep in the Sahara, the Algerian army ringed the natural gas complex where Islamist militants hunkered down with dozens of hostages Wednesday night after a rare attack that appeared to be the first violent shock wave from the French intervention in Mali. (AP Photo/NTB Scanpix, Kent Skibstad) NORWAY OUT

  • STATOIL

    Statoil spokesman Ole Anders Skauby, centre right, talks to TV reporters outside Scandic Bergen Airport hotel where a drop-in center is established for relatives of hostages involved in the situation in Algeria. Militants are holding a number of foreigners hostages in the Sahara desert in revenge for Algeria's support of French efforts to remove Islamists from control of neighboring northern Mali. (AP Photo / Hakon Mosvold Larsen / NTB scanpix) NORWAY OUT

  • An unidentified rescued hostage receives treatment in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013. Algeria’s state news service says nearly 100 out of 132 foreign hostages have been freed from a gas plant where Islamist militants had held them captive for three days. The APS news agency report was an unexpected indication of both more hostages than had previously been reported and a potentially breakthrough development in what has been a bloody siege. (AP Photo/Canal Algerie via Assiaciated Press TV) ** TV OUT ALGERIA OUT **

  • Residents of Ain Amenas, Algeria, gather outside the hospital trying to get information concerning relatives wounded during the terrorist attack at the gas plant, Friday, Jan. 18, 2013. The hostage crisis in the remote desert of Algeria is not over, Britain said Friday, after an Algerian raid on the gas plant to wipe out Islamist militants and free their captives from at least 10 countries unleashed bloody chaos. (AP Photo/Anis Belghoul)

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