Local governments in Gansu and Hebei provinces have tightened their COVID-19 pandemic control and prevention measures after sporadic outbreaks were reported.

In Lanzhou, Gansu, the bureau of education issued a notice ordering all schools, from kindergartens to senior high schools in the city, to temporarily suspend classes starting Thursday to prevent the spread of the coronavirus on campuses.

In addition, all teachers and students were ordered to be tested before the end of the day on Friday. No schools are allowed to resume classes until further notice, the notice said.

Meanwhile, all airline passengers are required to show negative results of tests done within 24 hours if they want to leave Gansu from the Lanzhou airport.

The notice was published after four new locally transmitted COVID-19 cases were reported in the northwestern province between Tuesday and Wednesday afternoon.

Gansu counted eight confirmed local infections of COVID-19, plus another two asymptomatic carriers, as of noon on Wednesday.

Seven confirmed cases and the two asymptomatic carriers were reported in Lanzhou, while the remaining confirmed case was detected in Zhangye.

Four tourists from a 20-member tourist group from Yunnan province tested positive when they arrived in Lanzhou, according to statement released early on Thursday morning.

Relevant departments have launched an epidemiological investigation and tracked close contacts, authorities said.

In Xingtai, Hebei province, two asymptomatic carriers were identified on Wednesday. The couple had arrived in Xingtai from Beijing to visit relatives, and investigators thought they might have brought the infection from other provinces, as they were similar to the confirmed cases in Beijing.

The pair were sent to a designated hospital for treatment and are said to be in stable condition.

"A total of 528,059 residents in the district completed their testing by 6 pm on Wednesday," said Qian Lixia, deputy mayor of Xingtai.