Shanghai reported one asymptomatic COVID-19 infection outside its quarantined population on Sunday, the city's health commission said at a news briefing.

The new infection is a 6-year-old who returned to Shanghai from Lhasa, Tibet autonomous region by flight MU2336 on Aug 9, said Zhao Dandan, vice-director of the commission.

A total of 396 close contacts and 509 secondary close contacts have been placed under quarantine, with the nucleic acid test results available as of 5 pm Sunday, all negative, Zhao said.

Epidemiological investigations showed over the past few days the patient has been to several places, including the Children's Hospital of Fudan University and the Ikea store in Xuhui district. Store personnel have been placed under two days of closed-loop management, followed by five days of health self-monitoring if no new infections are discovered, Zhao added.

The neighborhood where the new infection resides, on 580 Wanyuan Road in Minhang district, was listed as a high-risk zone for COVID-19.

As of Sunday, Shanghai has also received 30 flights with more than 5,000 passengers from Hainan province, where an ongoing COVID-19 outbreak has resulted in around 6,000 new infections since Aug 1.

All arrivals from Hainan will be subject to three days of home quarantine followed by four days of self-monitoring at home starting Monday, Zhao said. Those who do not fulfill the requirements for home quarantine can apply for quarantine at designated hotels, he added.

Zhao called on all those arriving in the city to strictly follow epidemic control protocol and report to the local public health authority within 12 hours of arrival if they come from areas at risk of COVID-19.

Shanghai, which experienced an outbreak of COVID-19 between March and May, also announced all kindergartens, primary and high schools will resume offline education on Sept 1 after a suspension on March 12.