Parents and guardians uninfected by COVID-19 are now allowed to accompany their quarantined children, a senior official of the Shanghai health authority told a news conference on Wednesday.

"Guardians who are not infected are allowed to accompany their infected children as long as they sign a letter of commitment and have a full understanding of the potential health risks," Wu Qianyu, a senior inspector of the Shanghai municipal health commission, said.

They are, however, required to wear masks, take personal precautions, dine separately, use separate daily necessities and adhere to the management and guidance of the health workers in hospitals, Wu said.

The official said that the authorities had also improved the services for infected children in other ways.

"First, we have strengthened our medical resources, set aside separate zones for the treatment of children, and allowed parents who are also infected to receive treatment while staying with their children," Wu said.

Shanghai's current largest makeshift COVID-19 hospital has set aside hundreds of beds to treat families with children under the age of 18.

The section of the temporary facility, built at the Shanghai New International Expo Center, started admissions on Monday and has received 177 people with infections, including 89 children, according to the Shanghai Children's Medical Center.

China's financial hub also launched another round of citywide antigen and nucleic acid testing on Wednesday in a bid to contain a recent resurgence of COVID-19 cases.

The city reported 311 confirmed locally transmitted cases and 16,766 local asymptomatic carriers on Tuesday, according to the municipal health commission.