China's local symptomatic coronavirus cases rose for a fourth consecutive day on Monday, with Xian city reporting more infections in a flare up that has put 13 million residents under lockdown.

Xian reported 175 symptomatic cases, up from the previous day's 150, official data showed on Tuesday.

No Omicron infections have been announced yet from the 810 confirmed cases in Xian from Dec. 9 to Monday. China has reported only a handful of Omicron infections among international travellers and in its south.

Nationwide, mainland China detected 182 local symptomatic cases for Monday, according to a statement by the National Health Commission, compared with 162 a day earlier and marks a fourth consecutive day of increase.

Monday's national local symptomatic case load also marks the highest daily count since the official daily bulletin started to classify asymptomatic carriers separately at the end of March last year.

Case numbers in Xian and in China are small compared with many clusters in other countries, but officials have imposed tough curbs on travel within the city and on leaving it, in line with the national guideline to immediately contain outbreaks.

Since last week, Xian residents have not been allowed to leave the city without clearance from their employer or authorities.

Officials have restricted permission for people to go out for necessary shopping during a new round of mass testing which started on Monday, and banned non-essential vehicles from entering roads.

There were no new deaths on Monday, leaving the national death toll at 4,636. Mainland China had 101,486 confirmed symptomatic cases as of end Dec. 27, including both local ones and those arriving from abroad.