China on Monday reported 76 new coronavirus cases, the highest daily rise since January, including 40 domestic transmissions prompting authorities to test millions in eastern Jiangsu province. 

Beijing has a zero-risk approach to the virus, which emerged in the central Chinese city of Wuhan in late 2019. It locks down cities and mass tests whenever small clusters appear.

Tens of thousands of people are under lockdown in Jiangsu's provincial capital Nanjing as authorities test the city's 9.2 million residents after an outbreak linked to its airport last week. 

"Of the 40 domestic cases, 39 were from Jiangsu province and one from Liaoning," the national health commission said in a statement Monday, adding there had been no new deaths.

Contact tracing also found five individuals who travelled through the Nanjing airport and tested positive after arriving in neighbouring Anhui and three other provinces, sparking fears that the cluster could lead to a fresh nationwide outbreak.

This prompted Nanjing officials to announce a second round of mass testing for all residents starting Sunday to identify patients who may take longer than usual to show symptoms. 

Beijing has rushed to curb recent mini-outbreaks in border provinces, aware of the risks of the fast-spreading Delta variant.  

One new case was reported Monday in the northeastern province of Liaoning that borders North Korea, bringing the total number of local transmissions in the region to five since Thursday.

Yunnan in the southwest has reported a spike in infections traced to neighbouring Myanmar, where the military government that seized power in February is struggling to contain a coronavirus surge. 

The province has reported 79 cases since June 20 with nearly half linked to Myanmar.

Beijing has tightened border controls and even supplied over 10,000 Covid-19 vaccines to the Kachin Independence Army, a spokesman for the rebel group said Saturday.

The border town of Ruili in Yunnan is using facial recognition to track people's movements and health status as they enter and exit residential areas, supermarkets, transport hubs and other public places to squash the virus spread.

The southern manufacturing hub of Guangdong is building a quarantine clinic for international arrivals with 5,000 beds after being hit by a recent virus outbreak.

China has recorded 92,605 virus cases and 4,636 deaths since the initial outbreak in late 2019.