As of Sunday, the number of confirmed and asymptomatic cases in Hainan had risen to 4,390 and 4,493 respectively since Aug 1. Sanya alone registered 3,305 confirmed and 4,006 asymptomatic cases, the Hainan Provincial Health Commission said on Monday.

Luo Dong, a vice-mayor of Sanya, said that the city has increased transport capacity and flights to ensure the orderly return of more tourists, and has adopted strict measures to prevent the epidemic from spreading elsewhere. He added that there have been no cases of spillover to other provinces and cities on the Chinese mainland since August.

Meanwhile, in Tibet, another region hit hard by the epidemic, the number of infections has continued to increase.

The Tibet autonomous region reported 77 locally confirmed COVID-19 cases and 755 asymptomatic carriers between Sunday and 2 pm Monday, health authorities said at a news briefing in Lhasa on Monday.

As of 2 pm Monday, the region has reported 160 confirmed and 1,326 asymptomatic cases.

"The Omicron variant BA.2.76 causing the outbreaks has a shorter incubation period, and is highly and rapidly transmissible, which enables hidden transmission, multi-chain transmission and cluster infections," said Wang Shoubi, an official from the region's health commission. "With the continuous improvement of the region's nucleic acid testing capability, we expect that hidden infections will be discovered and controlled more rapidly."

Separately, Beijing reported four new locally transmitted cases on Monday, including two with mild symptoms and two asymptomatic carriers, according to the local health commission.

The cases were reported in the districts of Changping, Chaoyang and Fengtai, according to Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control, at a news conference on Monday afternoon.

The infections were detected among people returning to Beijing and they have been sent to hospitals for treatment.

Residents who have been to high-risk areas including Hainan province, the Tibet autonomous region and the Xinjiang Uygur autonomous region should report to their residential communities, hotels or workplaces for epidemic prevention, Liu said.

"Epidemic prevention and control measures must not slacken as Beijing is facing a peak in returning travelers," he said.

Of the new cases, an asymptomatic carrier surnamed Liu has been investigated by Fengtai district police for allegedly concealing his travel history before returning to Beijing.

Liu was suspected of concealing the fact he had visited medium and high-risk areas, which led to 260 people designated as being at risk of infection.

Qiu Quanlin contributed to this story.