China reported a decline in new confirmed cases of the coronavirus in the mainland on Wednesday, but there was an increasing number of local transmissions in its far northeast bordering Russia.

China reported 46 new confirmed cases on Tuesday compared with 89 cases a day earlier, according to the National Health Commission. Of the new cases, 36 involved travellers arriving in China from overseas, compared with 86 a day earlier.

The 10 remaining cases were new locally transmitted infections, with Heilongjiang province accounting for eight of them and southern Guangdong province two.

In Beijing, where prevention measures remain stringent, an imported case from the United States was also reported on Tuesday, state television CCTV said. The patient started to show symptoms two days after arrival, despite testing negative initially.

The northeastern province of Heilongjiang has become a front line in China's fight to keep out imported cases as infected Chinese nationals return overland from Russia.

China has closed the border with Russia at Suifenhe, a city in Heilongjiang with a checkpoint into Russia.

New infections involving travellers arriving from Russia have also hit other parts of China such as the northern autonomous region of Inner Mongolia and the financial hub of Shanghai.

Some of the new confirmed cases had been asymptomatic. Two of the latest confirmed Heilongjiang cases on Tuesday were patients who showed no symptoms of the virus previously.

Heilongjiang reported one new asymptomatic case on Tuesday, a Chinese national returning from Russia. That brings the current number of asymptomatic cases in the province involving travellers arriving from abroad to 52.

In mainland China, the number of new asymptomatic cases increased to 57 on Tuesday from 54 a day earlier.

Over 6,700 asymptomatic cases have been reported since Jan. 28, of which 1,297 developed symptoms, while 4,444 still showed no symptoms after spending 28 days in quarantine, the National Health Commission told a briefing on Wednesday.

Over 1,000 people are still under observation, it said.

China does not include patients with no clinical symptoms such as a cough or a fever in its tally of confirmed cases.

The government has launched an epidemiological survey in nine regions in an effort to determine the full scale of asymptomatic infections and overall immunity levels, the official China Daily newspaper reported on Wednesday.

Chinese authorities said earlier in April that two-thirds of asymptomatic cases develop symptoms.

Central Hubei province, the origin of the coronavirus outbreak in China, reported just two asymptomatic patients who went on to develop signs of infection between March 31 and April 14.

Hubei province's health authority has reported 429 new asymptomatic cases since it began publishing data for such cases on April 1.

As of Tuesday, the total number of confirmed cases in mainland China had reached 82,295.

Authorities said 3,342 people have died from the virus in China, including one new fatality in Hubei.

China urged the United States on Wednesday to fulfil its obligations to the World Health Organization (WHO), after U.S. President Donald Trump halted funding to the body over its handling of the pandemic.

Foreign Ministry spokesman Zhao Lijian said the pandemic, which has infected nearly 2 million people globally, was at a critical stage and that Washington's decision would affect all countries.