BEIJING -- China is taking strict and swift measures to stem new COVID-19 infections that have emerged in multiple regions recently.

The Chinese mainland on Saturday reported 1,807 locally transmitted COVID-19 cases in 19 provincial-level regions, the National Health Commission (NHC) said Sunday.

Chinese Vice-Premier Sun Chunlan on Saturday urged regions experiencing severe epidemic outbreaks to clear COVID-19 cases among the general public in the shortest time possible.

Efforts should be made to expand the coverage of nucleic acid testing, accelerate epidemiological screening and patient transportation and isolation, and apply quarantine measures in a strict way, said Sun.

As part of the swift COVID-19 responses, China has added antigen detection as an option for COVID-19 testing among the public, in efforts to boost the early discovery of COVID-19 cases, the NHC said Friday.

Local authorities have also tightened measures to contain the new infections.

Shanghai on Saturday required citizens not to leave the city if not necessary and those who do must hold a certificate for a negative nucleic acid test results taken 48 hours before departure.

In the first two months of 2022, the megacity, with a population of nearly 25 million, has logged 1,243 confirmed COVID-19 cases arriving from outside the Chinese mainland, accounting for about 38 percent of total such cases on the mainland. The number is also roughly equivalent to 80 percent of Shanghai's total imported cases last year.

The city has required primary and secondary schools to switch to online classes and temporarily closed kindergartens and nurseries from Saturday after 11 locally transmitted COVID-19 cases and 32 imported cases were reported Thursday.

In Northeast China's Jilin province, which reported 1,412 local cases Saturday, local authorities have conducted multiple rounds of mass nucleic acid testing in face of the Omicron variant, which spreads easily and is hard to detect.

The city of Jilin conducted six rounds of mass nucleic acid testing and the Jiutai district in the provincial capital Changchun completed three rounds, while the rest of the city conducted two rounds.

Zhang Yan, deputy head of the provincial health commission, said the mass health screenings have allowed potential infections to be discovered in communities.

In face of the surging cases, the city of Changchun is building a makeshift hospital at an exhibition center that can provide more than 1,500 beds. In the city of Jilin, local authorities have built three makeshift hospitals, which can offer over 1,200 beds. The fourth one with over 2,000 beds is under construction.

Communities workers are in full swing to make sure COVID-19 prevention and control measures are implemented.

"We set up health checkpoints, organize nucleic acid tests, and deliver daily supplies to residents under quarantine during the day and work on shifts at night on epidemiological investigations, so we just slept in the office," said Shi Dan, a community worker in the city of Jilin.

"Despite this, no one backs down," she said. "We all want to win over the epidemic soon."