The man was a passenger on the Diamond Princess cruise liner in Japan, where dozens of passengers have become infected.
The Japanese Ministry of Health said the man was the sixth person from ship to have died. A Foreign Office spokesperson said it was supporting the family and in contact with Japanese authorities.
The uncertainty around the outbreak has sent stock markets plummeting — the worst week since the 2008 financial crash.
World Health Organisation (WHO) director general Tedros Adhanom Ghebreyesus described the global outbreaks as “linked epidemics”, adding there was no evidence coronavirus was spreading freely, stressing “we still have a chance of containing it”.
Across the UK, 20 people have now tested positive for the virus, with two new cases in England, one in Wales and another in Northern Ireland on Thursday night and one further case confirmed in England on Friday.
The UK’s chief medical officer Professor Chris Whitty said on Thursday it was “just a matter of time” before the virus began to spread within the UK.
Commenting on the most recent case, he said on Friday: “The virus was passed on in the UK. It is not yet clear whether they contracted it directly or indirectly from an individual who had recently returned from abroad. This is being investigated and contact tracing has begun. The patient has been transferred to a specialist NHS infection centre at Guy’s and St Thomas’.”
Travellers from northern parts of Italy have been told to self-isolate for 14 days with anyone worried they may have symptoms to contact the helpline NHS 111.
But The Independent has learned some callers are struggling to get through with long delays for call backs. On Thursday night, NHS England chief executive Simon Stevens said extra staff would be brought in to bolster the helpline.
One woman who returned from Italy recently and became ill earlier this week said she “had not had a call back since 10am on Thursday”, after she called again, an automated message was advising people to self-isolate.
She said: “The kids have been in school for days though we’ve tried to stay in. We ignored NHS 111 advice on Tuesday saying go to A&E and I’m glad we did.”
An NHS England spokesperson told The Independent: “While the service is understandably busy and people may have to wait longer than usual — all calls are being responded to thanks to hard working NHS staff.
“In addition, extra investment means the NHS is recruiting more call handlers to support those already working around the clock to give expert advice to callers on coronavirus and other medical concerns.”
Boris Johnson will hold a meeting of the government’s Cobra emergency committee on Monday but the PM has faced criticism for his “part-time” efforts.
The prime minister said on Friday that coronavirus was now top of the government’s agenda.
“On the issue of coronavirus, which obviously is a great concern to people, I just want to reassure everybody and say that the NHS is making every possible preparation,” he told Sky News.
“As you can imagine, the issue of coronavirus is something that is now the government’s top priority.
“I have just had a meeting with the chief medical officer and secretary of state for health talking about the preparations that we need to make.”
The shadow health secretary Jonathan Ashworth told the BBC there were serious concerns about capacity in the NHS, with just 700 spared beds during the past week.
The Labour MP said the government should consider emergency resources for the NHS to help it cope with any serious outbreak.
The former chancellor, George Osborne, said it was now time for the government to go on a “war footing” with daily NHS briefings for journalists.
The growing spread of the virus has also hit stocks and shares, which had their worst week since October 2008, at the time of the global financial crisis.
The Dow Jones was down 1.8 per cent on Friday with the FTSE 100 down 3 per cent.
A total of £210bn has been wiped off the FTSE 100 this week.
China has reported nearly 80,000 cases of coronavirus and almost 3,000 deaths, while the virus has reached nearly 60 countries and with more than 80 deaths.
“The outbreak is getting bigger,” WHO spokesperson Christian Lindmeier told a Geneva news briefing on Friday. “The scenario of the coronavirus reaching multiple countries, if not all countries around the world, is something we have been looking at and warning against.”
A dog in Hong Kong whose owner was infected with coronavirus also tested “weak positive” for the infection, the government said on Friday.
The Agriculture, Fisheries and Conservation Department (AFCD) said it was not yet clear that domestic pets could catch the virus or pass it on to their owners.