China's northeast Heilongjiang province which borders Russia has become the new battleground against the coronavirus as authorities reported the highest number of new daily cases in nearly six weeks, driven by infected travellers from overseas.

China fears a rise in imported cases could spark a second wave of COVID-19 and push the country back into a state of near paralysis.

A total of 108 new coronavirus cases were reported in mainland China on Sunday, up from 99 a day earlier and marking the highest number of cases since 143 infections were reported on March 5.

The National Health Commission said 98 of the new cases were imported, a new record. A total of 49 Chinese nationals who entered Heilongjiang province from Russia tested positive.

"Our little town here, we thought it was the safest place," said a resident of the border city of Suifenhe, who only gave his surname as Zhu.

"Some Chinese citizens they want to come back, but it's not very sensible, what are you doing coming here for?"

Though the number of daily infections across China have dropped sharply from the height of the epidemic in February, China has seen the daily toll creep higher after hitting a trough on March 12 because of the rise in imported cases.

Chinese cities near the border with Russia are tightening border controls and imposing stricter quarantines in response to influx of infected patients from the country.

Suifenhe last week announced restrictions on movements and gatherings similar to those imposed in Wuhan city, where the coronavirus outbreak first emerged late last year, and extended the closure of its border with Russia.

The land route through the city had become one of few options available for Chinese nationals trying to get into China after Russia stopped all flights to the country.

Suifenhe and Harbin, capital of Heilongjiang, are now mandating 28 days of quarantine for all arrivals from abroad as well as nucleic acid and antibody tests.

Streets in Suifenhe were virtually empty on Sunday evening due to restrictions of movement. Residents said a lot of people had left the city as the number of infected people crossing the border from Russia rose.

"I don't need to worry," Zhao Wei, another Suifenhe resident, told Reuters. "If there's a local transmission, I would, but there's not a single one. They're all from the border, but they've all been sent to quarantine."