A worker in a protective suit sprays disinfectant at a school in Inner Mongolia, China, in March 2020. (Reuters Photo)

A surge in new coronavirus infections in the northwestern Chinese city of Xian has prompted local authorities to announce stringent measures to contain further spread of the disease.

The city of 13 million, which entered its fifth day of lockdown on Monday, identified 150 new domestically transmitted cases with confirmed symptoms for Sunday.

That pushed the nationwide tally to 158, the highest since the country, where the highly-contagious virus first originated, managed to contain the outbreak in early 2020.

The official number of domestically transmitted cases with confirmed symptoms for Saturday was 155, showing a slight drop in the number of freshly detected cases.

However, the new cases have given rise to fears of a nationwide COVID-19 outbreak again.

Xian, with 485 local symptomatic cases reported for the December 9-25 period, has imposed stiff measures to control the outbreak.

The city managed to quickly detect those cases through three rounds of mass testing, He Wenquan, a Xian official, told a press conference on Sunday.

In order to quickly screen out the infected groups of people, after an analysis by experts, we will step up control measures in key areas, especially places with greater risk level, he added.

The authorities in Xian have urged residents to stay home except for collecting their test samples.

They have also launched a disinfection campaign, with workers spraying solutions onto roads and public and private buildings.

The city has announced no infections from the Omicron variant, although a handful of Omicron infections have been identified among international travellers and in southern China.

Since the start of the coronavirus pandemic, China has registered over 101,000 infections and less than 5,000 fatalities.

Meanwhile, 162 new symptomatic cases were detected across the Chinese mainland in the past 24 hours, according to official data.

This is the highest number of daily symptomatic infections in China since March 2020.