The number of Covid-19 cases in China reached the highest since March 2020 on Monday, as Beijing races to stamp out the highly transmissible coronavirus variant just three weeks before hosting the Winter Olympics.

China, where the virus first emerged in late 2019, has stuck to a strict policy of targeting zero Covid cases even as the rest of the world has re-opened.

But its approach has come under sustained pressure in recent weeks with multiple clusters across the country just as the Games are about to get underway in Beijing.

On Monday there were 223 cases more reported in China, including another 80 in the virus-hit port city of Tianjin, and nine more, including Omicron cases, in the key manufacturing hub of Guangdong.

Athletes and officials have already started to land in the capital ahead of the Games, immediately entering a tightly-controlled bubble that separates them entirely from the rest of the population.

But after a local Omicron case was detected over the weekend, authorities have also tightened regulations for those arriving in the capital from elsewhere in China.

Strain on economy

The city is now demanding a negative test before travel and a follow-up test after entering the city, with residents urged not to leave the city for the upcoming Lunar New Year holiday.

The infected woman has not travelled out of the city or had contact with other infected people, health officials said, as they tested some 13,000 people living or working in the same area.

Some tourist sites in the capital have also been closed.

Analysts have warned that the ongoing zero-Covid approach -- which includes swift and targeted lockdowns and travel restrictions  -- will increasingly weigh on the economy.

Another 68 cases were reported across central Henan province, where partial lockdowns and mass testing have been rolled out for millions of residents.

Zhuhai, the mainland city bordering the gambling hub of Macau, has told residents to avoid leaving the city after detecting a handful of Omicron cases and started testing the whole city from Monday.

Schools have also been closed.

Meanwhile, in the historic northern city of Xi'an, normally a popular tourist destination, infections have slowed to single-digit figures after nearly a month under lockdown.

Sixty more imported cases were also recorded Monday, as China maintains strict controls over border entry including slashed flight numbers and a "circuit breaker" policy where routes are halted if the number of infections brought in is too high.