Foreign Office (FCO) officials are investigating reports that a British national has died in Macedonia of suspected Ebola. If confirmed it would be the first death of a UK national from Ebola, although British nurse Will Pooley was cured of the deadly virus last month.
The news came as Downing Street said enhanced screening for Ebola will be introduced at Heathrow and Gatwick Airports and Eurostar terminals following advice from the Chief Medical Officer.
An FCO spokesman said: "We are aware of the reports and are urgently looking into them."
Mr Pooley, from Suffolk, became the first Briton to contract the virus after working as a volunteer nurse in Sierra Leone, which is one of the worst-hit countries of the current outbreak.
He was flown back to Britain on August 24 and recovered after being treated in an isolation unit at London's Royal Free Hospital. Meanwhile, new enhanced screening techniques will be introduced for passengers travelling from the main Ebola affected regions in west Africa - Liberia, Sierra Leone and Guinea - to give Britain an additional level of protection from the deadly virus.
The tests will involve assessing passengers' recent travel history, who they have been in contact with and onward travel arrangements as well as a possible medical assessment conducted by trained medical personnel. Contingency planning is also under way including a national exercise to make sure the country is fully prepared.
A Downing Street spokeswoman said: "Enhanced screening will initially be implemented at London's Heathrow and Gatwick Airports and Eurostar terminals and will involve assessing passengers' recent travel history, who they have been in contact with and onward travel arrangements as well as a possible medical assessment, conducted by trained medical personnel rather than Border Force staff. Passengers will also be given advice on what to do should they develop symptoms later.
"As the Chief Medical Officer's advice makes clear, these measures will help to improve our ability to detect and isolate Ebola cases. However, it is important to stress that given the nature of this disease, no system could offer 100% protection from non-symptomatic cases."
The advice of the Chief Medical Officer, Professor Dame Sally Davies, said it was right to consider further measures to make sure potential cases of Ebola are identified as quickly as possible in the UK. She said: "Although the risk to the UK remains low, in view of the concern about the growing number of cases, it is right to consider what further measures could be taken, to ensure that any potential cases arriving in the UK are identified as quickly as possible. Rapid access to healthcare services by someone infected with Ebola is not only important for their health but also key to reducing the risk of transmission to others.
"These measures could include a further UK-based package of measures to identify and assess the health status of passengers arriving from the affected countries and to ensure that those individuals know what to do should they be taken ill whilst in the UK."
The announcement follows confusion over whether the Government was introducing screening or not, amid calls for tests to be implemented after the United States put in place similar measures. Chancellor George Osborne had said screening would be introduced if medical experts deemed it necessary.
"If the medical advice is we need to screen - it might well be - then we will absolutely take that action," he told BBC News earlier.
Meanwhile, the Department of Health had insisted it had no plans for screening, while Defence Secretary Michael Fallon said the existing Government policy was in line with World Health Organisation (WHO) advice that exit screening was more effective.
A statement on the DoH website, now removed, had said: "The overall risk of Ebola to the UK remains low. Entry screening in the UK is not recommended by the World Health Organisation, and there are no plans to introduce entry screening for Ebola in the UK."
The introduction of tests follows calls for ministers to follow the lead of the United States which implemented screening at some airports.
MP Keith Vaz, chairman of the Home Affairs Select Committee, had called for screening and welcomed the news but said the Government must learn lessons from its "delay in action". He said: "I warmly welcome the Government's announcement which appears to be based on advice from the Chief Medical Officer. This now places us on the same page as the USA and South Africa, which began screening in April this year.
"We need targeted, enhanced screening to reassure the public and to relieve pressure on the Border Force. As to whether more should have been done sooner on this matter, the time for an inquiry is not now, but we must learn lessons from this delay in action."
A spokesman from the Macedonian foreign ministry said: "I can confirm that a British person has died and he is in the state hospital in Skopje. We are looking to see what are the reasons according to the protocols of the World Health Organisation."
The Macedonian foreign ministry spokesman confirmed that the Briton was travelling with a friend who is also currently in hospital, along with the ambulance crew that treated the man. He said: "There was a friend with him and he has also been retained in the hospital and the crew from the ambulance are also retained in the hospital."
Former foreign secretary David Miliband said there is no question that the West has been slow in its response to the crisis. Mr Miliband, who is in Sierra Leone with the International Rescue Committee which he heads, called on the "big guns" of the world to lend more support.
He told Channel 4 News: "There's no question that there's been a tardiness, a slowness, a lateness of response. The international agencies led by UN agencies have all said that. The summer period, the first case in this country was on May 26 and really it's only been over the last three or four weeks, two or three weeks, that there's been the kind of mobilisation that's necessary.
"My organisation, the International Rescue Committee, have been here for 15 years and we've got 200 staff in Sierra Leone, 200 in Liberia where I'll be visiting tomorrow. But in the end you need the big guns of the international system as well as a enjoined and focused local government if this kind of virulent disease is to be properly attacked."
The spokesman said the man who died had symptoms "similar" to Ebola but could not yet confirm whether he was carrying the virus.
Conservative MP Rory Stewart criticised the Government's screening plans, saying it does not make sense to only carry out tests at certain airports or train stations. He told Channel 4 News: "If we're moving into a situation in which we're seriously screening for an epidemic then we need to get it right across all ports of entry. It doesn't make sense to only screen limited places."
Mr Stewart, chair of the Defence Select Committee, said it was worrying that the West had been "distracted" by the situation in Iraq and Syria because this outbreak will set a precedent on how to deal with future epidemics, of which there will be more.
He said: "I think it is something that's a bit worrying. The New York Times has been reporting the Ebola virus very, very aggressively on its front pages for weeks now in a way that British newspapers haven't. I do think you're right - we've been distracted by Iraq and by Syria.
"This is so serious, it's serious from its own point of view but also as a precedent, we need to learn how to deal with these cases in the future. There will be more of these epidemics."