China has locked down 13m people in the central city of Xi’an, as the country battles to contain increasingly frequent coronavirus outbreaks that threaten its economic recovery in the run-up to the 2022 Winter Olympics.

The Xi’an city government ordered all residents to stay at home and designate one person per household to collect essential supplies once every other day. Non-essential travel outside the city has been banned, China’s official news agency Xinhua reported.

The lockdown is one of the most severe imposed in China since authorities restricted movement in Wuhan in early 2020 at the start of the global pandemic. It comes just months before the Beijing Winter Olympics, a politically sensitive event at which the government has banned visitors from overseas.

Leo Poon, a virologist at the University of Hong Kong, said that Chinese authorities wanted to ensure there was “zero risk” of the virus spreading across the country in the lead up to the Winter Games.

“They want to make sure the whole of China has minimal Covid activities,” he said. “With the presence of Omicron and Delta . . . this is going to be a challenge. ”

China reported a total of 73 new local cases of Covid-19 on Thursday, 63 of which were found in Xi’an. The country has so far administered almost 2.7bn doses of Covid-19 vaccines, according to government figures.

China recently contained an outbreak in the eastern province of Zhejiang, and this month introduced restrictions in the port city of Tianjin, which borders Beijing, after it discovered the country’s first case of the Omicron variant.

The Delta variant remains far more common than the new Omicron strain in China.