The latest COVID-19 outbreak in East China's Fujian province led to 263 confirmed infections and spread to four cities as of 8 am on Friday as mass testing continues.

Zhang Guoan, vice-director of the provincial health commission, said during a news briefing the 56 available results from genome sequencing all pointed to the highly contagious Delta variant.

About 60 percent of confirmed patients are in Putian, Fujian province, where the first case was detected on Sept 10. The neighboring city of Quanzhou had reported 18 cases, Xiamen, a popular tourist city, had registered 84 cases and Zhangzhou reported one case.

Putian had also detected nine asymptomatic carriers of the virus, Zhang added.

Wu Guoping, vice-director of the provincial education bureau, said all schools in the province are required to complete a new round of testing covering all students, faculty and staff members by Sunday.

Key groups will take one test every four days, and schools are encouraged to roll out more frequent tests within their capacity, he said during a news briefing on Friday.

Putian, Quanzhou and Xiamen had finished testing their teachers and students already, Zhang said, adding more than 80 percent of all teachers and students across the province had been tested.

China reported 62 new confirmed infections on Thursday, up from 49 cases the previous day.

In addition to the epidemic in Fujian, the Dehong Dai and Jingpo autonomous prefecture that borders Myanmar in Southwest China's Yunnan province reported one infection separately on Wednesday and Thursday.