A staff member checks the oral health of a student before she enters the kindergarten in Yongzhou on Tuesday. AFP

Officials had been ordered to submit by noon on Tuesday plans to administer nucleic acid tests on all residents in the city of 11 million people, according to an official notice carried by news outlets.

A nurse takes care of a patient at a hospital in Anlong county, in China's southwestern Guizhou province. AFP

"Each district should make plans and arrangements to conduct nucleic acid tests on the entire population in its jurisdiction within a 10-day time limit," the notice said, although it was unclear when testing would begin.

The planned tests come after Wuhan reported the first cluster of new COVID-19 infections since the city re-opened after a 76-day lockdown on April 8.

Six new cases were reported on Sunday and Monday from a residential compound in Dongxihu District.

Nurses recite an oath during a ceremony marking International Nurses Day, at Tongji Hospital in Wuhan. AFP

But an official from the Dongxihu District epidemic prevention and control commanding office said that they have "not yet received news about this notice."

China has largely brought the virus under control, but it has been on edge about being hit by a second wave as it has lifted lockdowns and restrictions across the country.

Virus clusters have appeared recent weeks in the northeastern provinces of Jilin and Heilongjiang, which border Russia.

With the virus taking hold in other nations, China has barred most foreigners from entering the country.

An elderly woman wearing a face mask piggybacks a boy along a street in Beijing. AFP

Wuhan has reported 3,869 deaths since the novel coronavirus first emerged there in December, accounting for most fatalities in China. Scientists believe the virus jumped from animals to humans at a market that sold wildlife in the city.

China's health authority said on Tuesday that the reappearance of local clusters of coronavirus cases in recent days suggests that counter-epidemic measures cannot be relaxed yet.

While prevention and control efforts have normalised, that does not mean measures can be eased, Mi Feng, spokesman at the National Health Commission, said at a media briefing.

Wuhan on Monday reported its first cluster of coronavirus infections since a lockdown on the city, the original epicentre of the outbreak in China, was lifted a month ago.