Five million residents of a central Chinese city started home confinement Tuesday in a new lockdown to curb the spread of the highly transmissible Omicron variant of the coronavirus, according to state media.

Beijing is on high alert for new outbreaks as it prepares to host the Winter Olympics next month, sticking to a "zero-Covid" strategy of targeted lockdowns, border restrictions and lengthy quarantines.

While those measures have kept the number of new cases far lower than virus hotspots in the United States and Europe, Beijing is currently battling local flare-ups in multiple cities.

The fast-spreading Omicron strain presents a fresh challenge, with two cases in Anyang -- the newly locked down city in Henan province -- linked to a growing infection cluster in the northern metropolis of Tianjin, some 400 kilometres (250 miles) away.

Authorities in Anyang announced the lockdown late Monday, issuing a notice ordering residents not to leave their homes or drive cars on the roads, state news agency Xinhua reported.

All non-essential businesses have been closed and a mass-testing drive has been launched "to respond to the severe epidemic control situation and strictly prevent the spread of the Omicron virus outbreak", Xinhua reported.

There were 58 new local infections reported in Anyang, state broadcaster CCTV said Tuesday, bringing the city's total caseload to 84 since Saturday.

Five million residents of central China's Anyang are underoing mandatory  coronavirus testing
Five million residents of central China's Anyang are underoing mandatory coronavirus testing AFP / STR

It was not immediately clear whether the new cases were tied to the Omicron variant.

The city had already restricted outbound travel, which local officials said was to "ensure that the outbreak does not spill over into outside areas".

At least three cities in Henan are battling emerging outbreaks, with provincial capital Zhengzhou closing schools and kindergartens, and stopping restaurants from accepting dine-in customers.

Last week, one million people in the city of Yuzhou were put under stay-at-home orders.

Elsewhere, Tianjin -- a major port city just 150 kilometres from Beijing -- has barred people from leaving without official permission, ordered the testing of all 14 million residents, and cancelled trains into the capital.

Tianjin is adjacent to Winter Olympics venues in Beijing and Hebei province and confirmed another 10 new locally transmitted cases after citywide mass testing.

The northern city of Xi'an is in its third week of lockdown as it attempts to stamp out a 2,000-case outbreak.

And after logging a handful of cases in recent days, Shenzhen -- a southern tech hub just across the border from Hong Kong -- has locked down some housing compounds, launched a mass-testing initiative and shuttered some long-distance bus stations.