The family of a British man who was shot dead on a beach in Libya said they are "shocked and devastated" by his killing.
A graphic picture of what purports to be the bodies of both energy worker Mark De Salis and a female friend from New Zealand, lying dead next to their picnic blanket, has been widely circulated on Facebook.
The bodies were discovered with gunshot wounds near the coastal area of Mellitah in the west of the country, according to a Libyan security source.
Mark De Salis, who has been named as the British man shot dead in Libya
The woman, who has not been named, was described as a "close friend" by De Salis' family.
De Salis, who had been working in working in Tripoli in Libya for six years, was remembered as a "decent and incredibly loyal man and he was loved by many".
In a statement, released through the Foreign Office, his family said: "The family of Mark De Salis are shocked and devastated to hear about Mark's death in Libya.
"Mark had been working in Tripoli in Libya for six years. He worked for First Engineering and was currently working as a power manager bringing generators to Tripoli to provide electricity. Mark enjoyed his work in Tripoli and liked the Libyan people.
"Mark enjoyed travelling and had travelled extensively. He was a decent and incredibly loyal man and he was loved by many. He will be sadly missed by his family and friends.
"Mark was with a close friend from New Zealand who was also killed and our thoughts are with her family at this sad time.
"We would ask that our privacy is respected at this time."
Mellitah is near the town of Zuwarah and 60 miles west of Tripoli.
The area is home to a large oil and gas complex co-owned by Italian company ENI.
Foreign Office officials have already urged the Libyan government to hold a "thorough investigation" into the murders, noting that its Charge d'Affaires has raised the shooting with the Libyan authorities.
The Foreign Office said they are liaising closely with them on follow-up, adding: "We call upon the Libyan government to carry out a thorough investigation into this tragic incident and to continue to do all it can to bring to justice the perpetrators of this appalling crime, as it strives to build strong rule of law in Libya."
The killings come a month after a US teacher was shot dead in the eastern city of Benghazi, after which the Foreign Office said further attacks against Westerners were likely.
Nearly two years after the overthrow of Colonel Muammar Gaddafi by rebels supported by British and French air strikes, the north African country has descended into a state of lawlessness as rival militias struggle for power and wealth.
The Foreign Office advises against all travel to most parts of Libya, including Benghazi, and against all but essential travel to coastal areas to the west and east, including Tripoli.
It warns of a "high threat from terrorism including kidnapping" in the country.
Last month Libya was named as one of the countries posing an ''extreme risk'' to human rights by UK-based risk analysis company Maplecroft in its annual Human Rights Risk Atlas.