The capital and largest city in northern China's Hebei province barred people from leaving on Thursday in an effort to curb the spread of the coronavirus.
The move came as the country reported the biggest rise in daily infections in more than five months.
Hebei accounted for 51 of the 52 local cases reported by the National Health Commission on Thursday. This compared with 20 cases reported in the province, which surrounds Beijing, a day earlier.
Authorities in Shijiazhuang, home to 11 million people, have launched mass testing drives and banned gatherings to reduce the spread of the coronavirus.
In addition to barring people from leaving the city, people and vehicles from areas of the city considered high-risk were not allowed to leave their district, authorities said.
Wartime mode
Hebei entered a "wartime mode" on Tuesday, meaning investigation teams would be set up at provincial, city and district levels to trace the close contacts of those who have tested positive.
Chinese state television earlier reported that Shijiazhuang had banned passengers from entering its main railway station. The city had previously required travellers to present a negative nucleic acid Covid-19 test result taken within 72 hours before boarding a train or a plane in the province.
Total new Covid-19 cases for all of mainland China stood at 63, compared with 32 reported a day earlier, marking the biggest rise in daily cases since 127 cases were reported on July 30th.
The number of asymptomatic carriers, who have been infected with the SARS-CoV-2 virus that causes the disease but have yet to develop any symptoms, also rose, to 79 from 64 a day earlier.
The total number of confirmed Covid-19 cases in mainland China since the outbreak first started in the city of Wuhan in late 2019 now stands at 87,278, while the death toll remained unchanged at 4,634.
In the city of Dalian in Liaoning province in China's northeast, which has reported local infections in recent days, residents in medium or high-risk areas have been barred from leaving the city. Residents in other areas were told to refrain from unnecessary trips out of Dalian.
Authorities in Guangdong province in southern China late on Wednesday reported a patient infected with a more transmissible variant of the coronavirus discovered in South Africa.
Some scientists worry that Covid-19 vaccines currently being rolled out may not be able to protect against this variant because of certain mutations that have been observed.
