Wuhan, the epicentre of the novel coronavirus outbreak in China, reported on Monday its first cluster of infections since a lockdown on the central Chinese city was lifted a month ago, stoking concerns of a wider resurgence of the disease.

The new infections sounded a note of caution amid efforts to ease coronavirus-related restrictions across China as businesses restart and individuals go back to work.

Also read: China's Wuhan, where the coronavirus emerged, begins to lift its lockdown

Wuhan reported five new confirmed cases, all of whom live in the same residential compound. One of them was the wife of an 89-year-old male patient reported a day earlier in the first confirmed case in the city in more than a month.

“At present, the task of epidemic prevention and control in the city is still very heavy,” said the Wuhan health authority in a statement. “We must resolutely contain the risk of a rebound.”

All of the latest confirmed cases were previously classified as asymptomatic, people who test positive for the virus and are capable of infecting others but do not show clinical signs such as a fever.

The number of asymptomatic cases in China is not known, as they only appear on the radar of health officials when they show up positive during tests conducted as part of contact tracing and health checks.

China does not include asymptomatic cases in its overall tally of confirmed cases, currently at 82,918, until they exhibit signs of infection. Mainland China has reported 4,633 deaths.

Hundreds of asymptomatic cases in Wuhan, which was released on April 8 from a months-long lockdown, are currently being monitored, according to the city’s health authority.

The number of new cases reported in China since April have been small compared with the thousands confirmed each day in February, thanks to a nationwide regime of screening, testing and quarantine.

The government said on Friday that China will gradually reopen cinemas, museums and other recreational venues, though restrictions including mandatory reservations and a limit on numbers will be in place.

Shanghai has already reopened some night entertainment venues such as discotheques. Walt Disney on Monday reopened its Shanghai Disneyland park to a reduced number of visitors.

New outbreaks in China in the past two months have mainly developed in residential compounds or at hospitals.

South Korea is also battling a wave of new cases, although the most recent outbreaks there started in nightclubs and bars.

‘War-time mode

The Wuhan cases helped push the overall new COVID-19 infections confirmed on May 10 to 17, the highest daily increase since April 28.

Northeastern Jilin province, which on Saturday reported a cluster of infections in one of its cities, Shulan, reported three additional local cases.

Shulan has been marked a high-risk area, the only place in China currently with that designation.

“We’re now in a ‘war-time’ mode,” said Jin Hua, mayor of Shulan, which until the weekend had reported no local cases for more than 70 days.

Shulan has imposed a lockdown on its 600,000 residents since the weekend, with just one member of a household being allowed out each day to buy necessities.

One of the three cases confirmed in the Jilin province on May 10 was from Shulan.

The other two were from the city of Jilin uncovered through contact tracing of people who were in contact with earlier Shulan cases.

Nearby Liaoning and Heilongjiang provinces each reported one case, adding to worries about a resurgence of the outbreak in the region.

A 70-year-old patient in Harbin, capital of Heilongjiang, had tested negative seven times before results turned positive.

Of the new cases, seven were so-called imported cases in the northern Chinese region of Inner Mongolia involving travellers from overseas.

Across China, the number of new asymptomatic COVID-19 cases fell to 12 on May 10 compared with 20 reported a day earlier.