The Foreign Office is warning Britons not to travel to mainland China, unless their journey is essential.
Its updated advice comes amid the coronavirus outbreak, which has caused more than 100 deaths, spread across China and to at least 16 other countries.
There have been no confirmed cases in the UK so far.
The FCO also advises against all travel to Hubei Province, saying anyone there who can leave should do so.
In its China advice on the gov.uk website, it said: “The FCO advise against all but essential travel to the rest of mainland China (not including Hong Kong and Macao).
“The Chinese government continue to impose further restrictions on movement within China in response to the coronavirus outbreak.
“It may become harder over the coming weeks for those who wish to leave China to do so. If you feel that you may want to leave China soon, you should consider making plans to do so before any further restrictions may be imposed.”
So far 97 people in the UK have tested negative for coronavirus, the Department of Health said, and there have been no positive results.
The FCO is arranging to evacuate Britons from Hubei province, where the virus was first detected.
Foreign Secretary Dominic Raab said the government was “working urgently to finalise arrangements for an assisted departure from Hubei Province for British nationals this week, and are in contact with people in Hubei to ensure they register their interest and that we can keep them updated”.
He added: “The UK continues to be guided by the latest medical advice about the coronavirus outbreak. The safety and security of British people will always be our top priority.”
Britons have also been advised by the FCO to “comply with any additional screening measures put in place by the local authorities”.
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It is thought people could be flown home as early as Thursday, with one teacher in Wuhan, the capital city of the province, telling the Press Association news agency that UK citizens were being given details of forthcoming flights.
Those in Wuhan and the surrounding areas have been urged to contact the British consulate before 11:00 local time on Wednesday if they wish to leave. Transport may come quickly and suddenly, officials have warned.
Up to 300 British people are thought to be in the city of Wuhan and in the wider Hubei province, which is now under strict travel restrictions.
Britons in parts of China affected by the virus have criticised the UK government for its lack of support over their return home.
Some in the Wuhan area said they had been given little information, compared to those from other countries. The US and Japan have been sending planes to Wuhan to evacuate their citizens.