The tally of new COVID-19 locally transmitted infections in Shanghai increased slightly on Friday after a few days of decline, as the city reported 2,736 local confirmed cases and 20,634 asymptomatic carriers.

According to Wu Qianyu, an official from the Shanghai Health Commission, the top five regions with the highest new infection increases from Thursday were Pudong New Area, Songjiang, Baoshan, Huangpu and Yangpu districts.

"Recent data indicated the city's epidemic situation is still at a critical, challenging stage," Wu said at a news briefing on Saturday.

The rise in data on Friday, Wu said, is concerned with cluster transmissions at construction sites, companies in operation, and old neighborhoods featuring shared facilities like bathrooms and kitchens.

"We'll toughen the prevention and control measures in related venues, strengthen self-health monitoring, mass screenings as well as disinfection," she added.

As of Friday, a total of 157 severe cases and 18 patients in critical condition are under treatment at designated hospitals. Twelve died with the average age of 88.2 years old, all with severe underlying conditions and diseases.