BEIJING, March 17 — China reported today another uptick in confirmed coronavirus cases as infections from abroad made it increasingly hard for authorities to reduce the overall number of new infections to zero.

Mainland China had 21 new confirmed cases yesterday, the National Health Commission said, up from 16 a day earlier. Of the new cases, 20 involved infected travellers arriving in China from abroad.

In contrast, mainland China only had one case of locally transmitted infection yesterday, in Wuhan, capital of central Hubei province where the flu-like disease appeared in humans late last year.

The number of infections imported from other countries surpassed local transmissions for a fourth day.

Beijing accounted for nine of the imported new cases, up from four on Sunday. The financial hub of Shanghai had three, up from two a day earlier.

Provinces reporting new infections from abroad include Guangdong, Zhejiang, Shandong, Guangxi, Yunnan and Shaanxi, bringing the total number of imported cases in mainland China so far to 143.

The Chinese capital has been the worst-hit even as it erected tough restrictions to screen out and isolate infections.

Beijing Capital International Airport has cordoned off a special zone for all international flights, with all disembarking passengers required to take health check-ups.

Transit passengers will be sent to their connecting flights, while non-transit passengers will be shuttled to a nearby processing venue from which they will be sent to designated places for compulsory 14-day quarantines.

Beijing has also redirected all international flights scheduled to land at its new Daxing airport in the south to the older Capital International Airport in the northeast.

The global tally of confirmed cases has exceeded 168,000, with China now accounting for less than half of that. The overall number of infections in mainland China stood at 80,881 as of yesterday.

The death toll in China had reached 3,226, up by 13 from the previous day.

In Hubei there were 12 new deaths, with Wuhan accounting for 11 of the fatalities. — Reuters