They were among 30 repatriated Britons and two Irish citizens beginning a 14-day quarantine at Arrowe Park Hospital in Wirral.

The four UK nationals caught the virus on the Diamond Princess liner in Japan, England's chief medical officer said.

They have now been transferred to specialist NHS infection centres.

Two patients are in the Royal Hallamshire in Sheffield, one is in the Royal in Liverpool and a fourth was transferred to the Royal Victoria Infirmary in Newcastle, NHS England said.

Prof Keith Willett, NHS strategic incident director for coronavirus said: "These specialist centres are well prepared to deal with cases and earlier this year the Newcastle unit successfully treated and discharged two patients who had contracted the virus."

Prof Willett added there had been a "calm response" to confirmed cases of coronavirus so far, "which will continue to be important as more of us might need to self-isolate for a time, to protect ourselves, our families and the community".

Prof Keith Neal, emeritus professor of epidemiology of infectious diseases at the University of Nottingham, said the four new cases were not surprising and would present no risk to the public.

The Department of Health said a "full infectious disease risk assessment" was done before Saturday's repatriation flight from Japan, adding that no-one who boarded the flight had displayed any symptoms of the virus.

Any more passengers who test positive will immediately be taken into specialist NHS care, the department said.

It added that "appropriate arrangements" are in place at Arrowe Park, including strict separation of passengers from staff and from each other.

It comes as 118 UK citizens and their family members rescued from Wuhan - the centre of the virus outbreak - ended their two-week isolation in Milton Keynes on Sunday.

Last weekend, NHS England announced that all but one of the nine people being treated for the coronavirus in the UK had been discharged from hospital.

Analysis

by BBC News medical correspondent Fergus Walsh

It's not surprising that some of those repatriated from the Diamond Princess have tested positive for the coronavirus.

They were on board a ship where the quarantine was a failure - more than one in five of the 3,700 passengers and crew have tested positive.

In the US, 18 repatriated passengers from the cruise ship subsequently tested positive for Covid-19, as did seven passengers flown back to Australia.

It would seem likely that more of those in quarantine in Arrowe Park hospital may test positive in the coming days.

But the NHS is well able to cope with such cases and can isolate and treat patients in specialist centres.

Far more concerning is the situation in Italy, Iran and South Korea, where there is human-to-human spread of the virus in the community, which could eventually lead to the World Health Organization declaring a pandemic.

Arrowe Park Hospital was previously used to isolate 83 British nationals who were flown back to the UK from Wuhan on the Foreign Office's first evacuation flight in January.

Janelle Holmes, chief executive at Wirral University Teaching Hospital NHS Trust reassured staff that the hospital was "running as usual".

"When guests arrived yesterday evening, we followed clear guidance in relation to infection prevention control. This was to minimise the chance of any infection spreading."

The evacuees had already spent two weeks in quarantine on board the cruise ship, but since then 600 passengers and crew have tested positive for the new virus, raising fears that the incubation period for the virus may be longer than originally thought.

Separately, four Britons from the ship who recently tested positive for the new coronavirus were not on Saturday's repatriation flight.

They included David and Sally Abel, from Northamptonshire, who have since been diagnosed with pneumonia, according to their family and are being treated in a Japanese hospital.

Relatives said the couple are both "having a really tough time" and feel "very much in the dark" in terms of treatment, adding that they are awaiting further tests.


Italy imposes lockdown

The new strain of coronavirus, which originated last year in Hubei province in China, causes a respiratory disease called Covid-19.

China has seen more than 76,000 infections and 2,442 deaths. The virus has since spread to at least 11 other countries.

Over the weekend, Italian officials imposed strict quarantine restrictions in two northern "hotspot" regions close to Milan and Venice, as the number of coronavirus cases soared to 130 - the worst outbreak in Europe.

Venice Carnival has been cut short, schools and museums closed and sporting events suspended as authorities struggle to contain the spread of the virus.

About 50,000 people cannot enter or leave several towns in Veneto and Lombardy for the next two weeks without special permission. Three people have died.

Elsewhere, authorities in South Korea and Iran are battling to control rising numbers of infections.

South Korea has raised its coronavirus alert to the "highest level". The UK Foreign Office has advised against all but essential travel to the cities of Daegu and Cheongdo.

Turkey, Pakistan and Afghanistan have closed their borders with Iran, where eight people are known to have died. Officials have ordered the closure of schools, universities and cultural centres in 14 provinces.