WUHAN, China (Reuters) - A growing number of imported coronavirus cases in China risked fanning a second wave of infections when domestic transmissions had “basically been stopped”, a senior health official said on Sunday, while eased travel curbs may also add to domestic risks.

A man wearing a face mask skateboards on a street in Wuhan, Hubei province, the epicenter of China's coronavirus disease (COVID-19) outbreak, March 28, 2020. REUTERS/Aly Song

China, where the disease first emerged in the central city of Wuhan, had an accumulated total of 693 cases entering from overseas, which meant “the possibility of a new round of infections remains relatively big”, Mi Feng, spokesman for the National Health Commission (NHC), said.

Nearly a quarter of those came from arrivals in Beijing.

“Beijing, the capital, still bears the brunt of the risks,” said Xu Hejian, spokesman for the Beijing government, told reporters.

“There’s no reason to lay back and relax yet. It’s not a time when we can say everything is going well.”

Most of those imported cases have involved Chinese returning home from abroad.

A total of 3,300 people have now died in mainland China, with a reported 81,439 infections.

China was widely accused of a delayed response when suspected cases first emerged in December, with a young doctor reprimanded for “spreading rumors” when he tried to raise the alarm.

But the world’s most populous country has since won praise from the World Health Organization for its efforts to lock down affected areas and isolate patients.

In the last seven days, China has reported 313 imported cases of coronavirus but only six confirmed cases of domestic transmission, NHC’s data showed.

There were 45 new coronavirus cases reported in the mainland on Saturday, down from 54 on the previous day, with all but one involving travelers from overseas.

Airlines have been ordered to sharply cut international flights from Sunday. And restrictions on foreigners entering the country went into effect on Saturday.

Five more people died on Saturday, all of them in Wuhan, the capital of Hubei province. It has reported only one new case in the last 10 days.

Saturday marked the fifth consecutive day that Hubei recorded no new confirmed cases. The sole case of domestically transmitted coronavirus was recorded in Henan province, bordering Hubei.

On a cold and rainy Sunday, Wuhan streets and metro trains were still largely empty. The Hubei government said on its official WeChat account that a number of malls in Wuhan, as well as the Chu River and Han Street shopping belt, would be allowed to resume operations on Monday.

With traffic restrictions in the province lifted, Wuhan is also gradually reopening borders and restarting some local transportation services.

“It’s much better now,” a man, who gave his surname as Hu, told Reuters as he ventured out to buy groceries in Wuhan.

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All airports in Hubei resumed some domestic flights on Sunday, with the exception of Wuhan, which will open to domestic flights on April 8. Flights from Hubei to Beijing remain suspended.

A train arrived in Wuhan on Saturday for the first time since the city was placed in lockdown two months ago.

Restrictions have also been eased on people looking to return to the capital, although the procedure still appears much more vigorous as it’s done on an application approval basis.

More than 7,000 have returned to Beijing from Hubei by charted trains or private cars, Mao Jun, a Beijing government official, said on Sunday.

But as travel restrictions are rolled back, concerns about asymptomatic cases have intensified. Gansu, a province in northwestern China, reported a new case on Sunday of a traveler from Hubei who drove back on a health code declaring the person free of virus.

It is unclear how the person became infected, according to the report by state broadcaster CCTV.

As scientists worldwide scramble to fight the battle against the coronavirus, a Chinese research institute said this week it has developed a nanomaterial that can absorb and deactivate the coronavirus, and that it is looking to work with companies to apply the technology in making air purifiers and face masks.

Lab tests by a CDC branch in China’s Anhui province showed the material deactivated 96.5-99.9% of the coronavirus, the Dalian Institute of Chemical Physics under state think tank Chinese Academy of Sciences said in a statement.

(This story corrects paragraph 14 to state that Hubei reported zero new coronavirus cases for the fifth consecutive day on Saturday, not fourth consecutive day as previously stated)