Shenzhen has discovered BF.15 — a new mutation of the omicron subvariant BA.5.2.1 — among the city's COVID-19 infections since Aug 23, the first time the new mutation appeared in the city, a senior health official said.

Other infections were related to omicron subvariants BA.5.2, BA.5.2.1 and BA.2.2, all of which are contagious and harder to discover, said Lin Hancheng, a senior member of Shenzhen's health commission.

"The mutant strains found in the COVID-19 cases are highly homologous with some of the strains reported overseas," Lin said during a news conference on Monday. "As a result, the possibility that the latest COVID-19 flare-up was caused by imported cases cannot be ruled out."

On Monday alone, Shenzhen reported 35 new COVID-19 infections, of which 24 were confirmed as locally transmitted and 11 asymptomatic carriers, according to the local health authority on Tuesday.

The new cases covered the districts of Futian, Luohu, Nanshan, Longgan and Yantian.

Shenzhen Mayor Qin Weizhong chaired a meeting on Monday and urged efforts to stem the spread in the shortest time possible and hold firm the bottom line that there would be no large-scale COVID-19 rebound in the city.

Restaurants and canteens in the Futian and Luohu districts have been ordered to limit their operating capacity and service hours, and to temporarily halt dine-in services for four days, Monday to Thursday.

Meanwhile, all deliverymen in the two districts are prohibited from entering residential communities and urban villages, and takeaways and packages should be placed at designated locations for collection.

Large conferences, activities, forums, performances, sales promotions, fairs and square dancing have been halted. Parks in the two districts are temporarily closed.

Wholesale markets and indoor recreational facilities were ordered to suspend business. Education and training institutions should halt in-person operation in Futian and Luohu.