China has confirmed its first significant Covid-19 outbreak for six months, as authorities struggle to contain the Delta variant in an outbreak linked to an airport in the aastern city of Nanjing.

The National Health Commission recorded 64 new cases in the mainland for July 29, compared with 49 cases the day before. There were no deaths.

The first cases were reported among staff and travelers passing through Nanjing's airport, which serves 30 million passengers annually. According to officials quoted in China news media, airport staff may have been infected as a result of incorrect waste disposal - although they didn't specify how the virus got there.

"We should take special measures on high-risk groups, such as those at entry ports, when it comes to tests, discovery, tracing and vaccination," Shao Yiming of the Center of Disease Control, said at a news conference.

According to the Global Times, which cited unidentified sources, all flights at the Nanjing airport will be suspended until Aug. 11. It said airport officials hadn't ruled out a prolonged suspension.

Authorities have undertaken extensive testing in the city and the airport was closed Tuesday.

Early Wednesday a number of high-ranking provincial party leaders, governors and health officials met in Jiangsu to discuss the outbreak, according to CNN.

The Provincial Committee of the Communist Party of China acknowledged the current outbreak was "severe," and said the Nanjing cluster might affect the "whole country" in a news release posted on its website.

The statement called for tougher preventative and containment measures, such as "closed communities and enclosed areas" - an appeal to reimpose restrictions more than a year after China loosened its statewide lockdown and reopened businesses.

It said there had been 92,875 confirmed coronavirus cases in mainland China as of July 29.

The death toll from the coronavirus in China is 4,636.