The Chinese city of Xi'an remained under lockdown for a fifth day on Monday as authorities reported 150 new local symptomatic coronavirus cases for Sunday, a slight decrease from the previous day.

Case numbers in Xi'an, home to 13 million people, remain tiny compared with many clusters overseas, but authorities have imposed tough curbs on travel within and leaving the city under Beijing's drive to immediately contain outbreaks.

Authorities have not announced any infection caused by the omicron variant in Xi'an, where there have been 635 confirmed coronavirus cases during the Dec. 9-26 period. The 150 local symptomatic cases on Sunday compared with 155 a day earlier, and accounted for most of the 162 new domestic infections in China.

China reported a total of 158 domestically transmitted symptomatic cases for Sunday.

Nationwide, China has detected a handful of omicron infections among international travelers and in South China.

The new case number for Sunday marks the highest nationwide count of local symptomatic infections since the daily bulletin provided by the National Health Commission (NHC) started to classify asymptomatic carriers separately from end-March 2020.

In Xi'an, residents cannot leave the city without approval from employers or local authorities.

Since Dec. 23, households have been allowed to send only one person to shop for necessities every two days. Other family members may not leave home unless they have essential jobs or urgent matters to attend to, approved by employers or communities.

On Monday, Xi'an authorities urged residents to stay home except for having their sample collected in a new round of citywide testing.

Xi'an has also launched a city-wide disinfection campaign, with workers spraying pathogen-killing solutions onto roads and buildings, and residents were advised not to touch plants or building surfaces.

Dongyan Jin, a virologist at the University of Hong Kong, said the mass disinfection of outdoor air and surfaces seemed unnecessary given the low risk of people catching COVID-19 from outdoor surfaces or air with so few people outside.

"This is shooting mosquitoes with cannon," said Jin, although he believes disinfection of indoor surfaces, especially in places visit by infected people, is necessary.

The cities of Xi'anyang and Weinan, like Xi'an in Shaanxi province, each reported one local symptomatic case for Sunday. Local infections were also found in the Guangxi region and the provinces of Zhejiang, Guangdong and Sichuan.