China reported on Tuesday an increase in cases of the new coronavirus coming from abroad, as the country where the disease first emerged now worries about importing infections.

In total there have been 13 confirmed cases of the virus being imported into the mainland -- all Chinese nationals returning from overseas.

More than 3,100 people have died and over 90,000 have been infected worldwide.

The vast majority of cases are in China but South Korea, Italy and Iran have emerged as the countries with the most cases outside the epicentre.

Eight Chinese nationals who worked in the same restaurant in Italy's northern Lombardy region have tested positive for the virus in eastern Zhejiang province, according to the local government.

There have also been four confirmed cases travelling back from Iran -- two in Beijing and two in the northern Ningxia region -- plus one case in the southern city of Shenzhen who had travelled from the UK via Hong Kong.

Beijing has been implementing a series of measures to try and prevent its containment efforts being undone by imported cases carried into the country.

Hundreds of passengers from South Korea arriving in eastern China were placed in isolation after people on two flights were discovered to have fevers last week.

No infections have been confirmed so far.

Those arriving in the capital city from virus-hit areas are being made to self-quarantine for 14 days.

On Tuesday officials in the city of Dandong, which borders North Korea, announced that everyone coming into the city from overseas will have to be tested for the coronavirus.