About 1.2 million people in Xiong'an New Area -- a new economic zone 100 kilometres southwest of China's capital -- are no longer allowed to enter or leave their residential compounds, local virus prevention staff confirmed to AFP on Friday.

While recent lockdowns in China are publicly announced and widely reported by state media, the Xiong'an restrictions appear to have been introduced without notice -- sparking confusion among some residents of the area.

"We expect this (lockdown) to last around a week, but the exact timing is uncertain," said virus prevention staff in Xiong County, one of three counties in the area.

The restrictions kicked in on Tuesday, they added -- the same day authorities in another district noted five confirmed coronavirus infections had been discovered to date.

With the Winter Olympics beginning next week, Chinese authorities have scrambled to eradicate flare-ups in several major cities, including Beijing.

China reported 39 domestic Covid-19 cases on Friday, including a new Omicron cluster in the eastern city of Hangzhou, home of e-commerce giant Alibaba.

Some 22 infections had been detected in Hangzhou as of Friday, and local health officials warned of further cases after one patient was found to have attended a gathering of more than 300 people.

Officials in Suifenhe, a city in Heilongjiang province along the Russian border, were also racing to stamp out a mini-outbreak linked to the Delta variant.

The latest string of flareups has put spring festival holiday plans for millions of people at risk.

Olympic bubble

Some users on China's Twitter-like Weibo platform were seen asking for further information about restrictions, while others questioned the extent of the measures.

"Is there a need? Why can't we go home if the area is deemed low-risk? Don't make this one-size-fits-all," said one Weibo user this week.

Another said Thursday: "I don't think I'll be able to go home for the Lunar New Year."

Meanwhile, the Winter Olympics will be held in a strict "closed-loop" bubble that separates everyone involved in the Games from the wider Chinese population in a bid to reduce the risk of infections leaking out.

Two athletes and eights officials arriving in China tested positive for the virus on Thursday, pushing the total number of positive cases to 89.

China, where the coronavirus first emerged, maintains a strict "zero-Covid" strategy involving targeted lockdowns, tight border controls and mass testing.

Its case numbers are tiny in comparison to the rest of the world.

A month-long lockdown on the megacity of Xi'an was lifted earlier this week after a cluster that grew to more than 2,100 cases -- China's largest outbreak in months -- was largely stamped out.

But stubborn flare-ups have persisted, including in Beijing and the nearby port city of Tianjin.