China has approved early-stage human tests of two experimental vaccines to combat the new coronavirus as the country where the virus was first detected battles to contain imported cases, especially from Russia.

Russia has become China’s largest source of imported cases, with a total of 409 infections originating in the northern neighbour. Chinese people there should stay put and not return home, the state-owned Global Times said in an editorial on Tuesday.

“Chinese people have watched Russia become a severely affected country ... This should sound the alarm: China must strictly prevent the inflow of cases and avoid a second outbreak,” said the paper, which is run by the Communist Party’s People’s Daily.

China’s northeastern border province of Heilongjiang saw 79 new cases of imported coronavirus cases on Monday, all Chinese citizens travelling home from Russia, state media said. Mainland China reported 89 new cases.

Heilongjiang’s provincial authority said on Tuesday that it had established a hotline to reward citizens as much as 5,000 yuan ($710) for handing over or reporting illegal immigrants.

China has reported 82,249 coronavirus cases and 3,341 deaths. It reported no new deaths on Tuesday.

Mongolia's health ministry also confirmed 13 new cases, all imported from Russia.

As China fights to prevent a second wave of coronavirus infections, two experimental vaccines will be tested on humans, the Xinhua state news agency reported.

They are being developed by a Beijing-based unit of Nasdaq-listed Sinovac Biotech and by the Wuhan Institute of Biological Products, an affiliate of state-owned China National Pharmaceutical Group.

In March, China gave the green light for another clinical trial for a vaccine candidate developed by China’s military-backed Academy of Military Medical Sciences and Hong Kong-listed biotech firm CanSino Bio.

US drug developer Moderna said earlier it had begun human tests of its possible vaccine with the US National Institutes of Health.

But even as hopes for a vaccine are raised, the epidemic could stretch on for up to two years, and precautions such as masks and preventing big gatherings may need to continue, Zhang Boli, an academic at the Chinese Academy of Engineering and president of the Tianjin University of Traditional Chinese Medicine told reporters.

“We have to make preparations for the long term,” he said.

At a meeting chaired by Premier Li Keqiang on Monday, China’s coronavirus task force decided to deploy more health resources on borders.

It said it would build hospitals and establish isolation points near borders and also strengthen cooperation with neighbours.

However, officials acknowledged that China’s extensive border with numerous country roads, paths, ferry crossings and mountain passes made it difficult to control.

o ensure no infected people slip in from Russia, China has put in stringent measures in Suifenhe, a small city in Heilongjiang with a checkpoint into Russia. Train services from it have been reduced and cars need a special pass to leave.

Piao Minghua, deputy head of customs in the area, said everyone entering Suifenhe had to be tested for the coronavirus, give details of contacts and undergo quarantine.

City residents are only allowed to leave their homes once every three days, many shops are closed and markets largely deserted.

Though the northeast border remains China's priority, state media also reported late on Monday that more than 100 people had been arrested in March for illegally entering China through its southwestern border in Yunnan province.

Thousands of people, mostly Chinese workers and traders, were flooding back into Yunnan from Laos and Myanmar this month, putting huge pressures on border regions like Xishuangbanna. ($1 = 7.0478 Chinese yuan)