A total of 138 people in Kashgar prefecture of the Xinjiang Uygur autonomous region have tested positive for COVID-19 as of Sunday, local health authorities said.

Gu Yingsu, deputy director of Xinjiang's health commission, said they are all asymptomatic cases.

The first reported asymptomatic case, a 17-year-old female villager from Shufu county, tested positive for the virus during the county's routine nucleic acid testing on Saturday and the other 137 asymptomatic cases were found on Sunday. They were all related to the factory where the girl's parents work, Gu said at a news conference in Urumqi.

The villager has not left Kashgar since the beginning of this year. Her brother and parents tested negative.

All asymptomatic COVID-19 patients have been quarantined for medical observation at a designated hospital in Kashgar and show no signs of fever or coughing, Gu said, adding that all of their close contacts have been quarantined.

Kashgar has started to offer nucleic acid testing to all residents in the area, and more than 2.8 million of the over 4.7 million residents of Kashgar had been tested as of 2 pm on Sunday, she said.

Shufu completed testing all of its residents on Sunday, while other areas of Kashgar are expected to complete their testing on Tuesday, Gu said.

All highways, railways and the airport remain operational in Kashgar, she said. Visitors to the city do not have to be quarantined or show nucleic acid test reports, but people who leave the area should have tested negative for COVID-19 within the past seven days, she added.

The National Health Commission sent a work group to Kashgar on Sunday to guide epidemic prevention and control work.

All non-boarding kindergartens and primary and secondary schools in Kashgar will suspend their classes from Monday to Friday. Supermarkets and shopping malls will remain open to ensure sufficient supplies of daily necessities, the Kashgar publicity department said.

Chen Quanguo, Party secretary of Xinjiang, said the region should race against time and work hard to prevent the spread of the pandemic.

Chen made the remark at a videoconference held on Saturday night to discuss containment measures, adding that the region should attach great importance to virus prevention and control work in Shufu and safeguard the health of people of all ethnic groups.

Officials should always be vigilant and ensure all containment measures are implemented in a targeted and scientific manner, he added.

Xinjiang had a cluster of infections mainly in Urumqi, the regional capital, in July and August, but no new cases had been found in the region since Aug 18.

The Beijing Center for Disease Prevention and Control advised residents on Sunday not to travel to Kashgar unless necessary.