SHANGHAI -- China's economic hub Shanghai is conducting a new round of screening using both nucleic acid and antigen testing to contain the latest resurgence in COVID-19 infections, a municipal health official told a press conference on Wednesday.

As of 10 am Wednesday, around 9.1 million residents had undergone nucleic acid testing in many areas of the city including those on the east of the Huangpu River that are under temporary closed-off management, said Wu Qianyu, an official with the Shanghai Municipal Health Commission.

Meanwhile, some 10.87 million residents had taken antigen testing to screen for COVID-19 infections by Wednesday morning.

The megacity with a population of over 24 million on Monday began enforcing temporary closed-off management in two phases to track possible infections and curb the spread of the virus.

Starting from Wednesday, Shanghai will carry out a large-scale disinfection lasting one month in key places, such as office buildings, construction sites, transport vehicles, farm markets and residential communities, according to the press conference.

Minister warns against relaxing antivirus measures

The Chinese mainland reported 1,565 locally transmitted and confirmed infections and 7,090 asymptomatic cases on Tuesday, according to the health commission.

Shanghai, which entered a phased lockdown on Monday to facilitate a citywide screening campaign, registered a record high of nearly 6,000 COVID-19 infections on Tuesday, including 326 confirmed cases and 5,656 asymptomatic cases.

Wu Qianyu, an official with the Shanghai Municipal Health Commission, said during a news conference on Wednesday that daily new infections remain at a high level, putting enormous pressure on its medical institutions. To ease the strain, new quarantine facilities have been put into use and several more are currently being built.