The Chinese mainland recorded 55 new locally transmitted confirmed cases of COVID-19 on Tuesday, the lowest daily number since Jan 11.

The lion's share came from Heilongjiang province. Data from the provincial health commission showed 29 new confirmed cases were detected, with 12 in Harbin, the provincial capital, and 17 in Wangkui county in Suihua. The province also detected 28 asymptomatic cases on Tuesday, all in the two areas.

Six areas in Suihua, including Wangkui, will continue to conduct strict lockdown for another seven days, officials said on Wednesday.

"Over the past seven days, residents in these areas, where positive cases were reported, have stayed at home in self-quarantine," Guo Jianmin, director of the city's health commission, said. "To lower the risk of virus spread, experts advised that the quarantine period should be prolonged."

As the number of COVID-19 cases has soared in Heilongjiang, local enterprises are continuing epidemic prevention and control efforts, including beefing up testing capacity.

Twelve white, tent-like inflatable facilities have been built at a laboratory in Harbin operated by Shenzhen-based biotech company BGI Genomics. They will boost the lab's testing capacity to more than 20,000 tubes of samples a day, local media reported on Wednesday.

Meanwhile, workers at Harbin Dahuanghuanyu New Technology are busy producing a new disinfectant.

"It contains more environmentally friendly ingredients without an unpleasant or irritating odor," said Sun Zhichao, head of the company's factory. The company's daily output has increased by 50 percent to meet demand and guarantee supplies.

As of Tuesday, there were 486 confirmed cases and 529 asymptomatic carriers in Heilongjiang.

Neighboring Jilin province recorded 14 new confirmed cases on Tuesday, driving its caseload to 294, the provincial health commission said.

A work team led by Gao Guangbin, deputy Party secretary of Jilin, has arrived in Tonghua, which was heavily affected by the recent outbreak, Jilin Daily reported. As of Tuesday, there were 204 confirmed cases and 74 asymptomatic carriers in the city.

The provincial finance department is promoting a subsidy policy for medical and epidemic prevention workers in major affected areas.

"Medical workers on the front line will receive a subsidy of 600 yuan ($93) per day and the others will receive 400 yuan per day, double the national standard," said Wang Huiqun, deputy director of the department.

Beijing recorded four new confirmed cases and one asymptomatic carrier on Tuesday.

All of the confirmed cases were in a residential community in Daxing district, where a number of cases have emerged lately, the capital's health commission said.

To further curb the risk of imported cases, Beijing said people from low-risk areas in the country who plan to visit Beijing from Thursday to March 15 should bring a negative nucleic acid test result taken within seven days of their arrival, said Xu Hejian, spokesman for the Beijing municipal government, adding that people from medium-and high-risk areas and ones where communities are under lockdown management should not visit Beijing during the period unless they get approval from their provincial virus control and prevention department.

In Shanghai, one new local case was detected on Tuesday. There are clear epidemiological links between all 16 locally transmitted COVID-19 cases in Shanghai, and none of them contracted the virus from an unknown contact, said Wu Jinglei, director of the city's health commission.

Hebei province recorded seven new confirmed cases on Tuesday, the second day with a single-digit rise since Jan 4.

Du Juan in Beijing, Zhou Wenting in Shanghai and Han Junhong in Changchun contributed to this story.