A Chinese city of 3.5 million near the border with Vietnam was on lockdown Monday after more than 70 coronavirus cases were discovered there over the past three days.

China, the only major world economy still sticking to a staunch zero-Covid policy, is on high alert for any outbreaks as it hosts the Beijing Winter Olympics.

Local officials in the city of Baise in the southern Guangxi region announced Sunday that no one would be allowed to leave the city, while residents of some districts would be confined to their homes.

"Citywide traffic controls will be implemented," vice-mayor Gu Junyan told a briefing.

"In principle, vehicles and people cannot enter or leave the city… with personnel control strictly enforced and no unnecessary movement of people."

Residents of some neighbourhoods in smaller rural cities and counties under Baise's jurisdiction have been placed under strict home confinement, while others cannot leave their district, Gu added.

Baise, located about 100 kilometres (62 miles) from the Vietnamese border, on Friday discovered its first local case — a traveller who had returned home for the week-long Lunar New Year holiday, according to officials.

Since the pandemic, China has built a heavily enforced wire mesh fence along its southern border to keep out illegal migrants from Vietnam and Myanmar — as well as potential Covid-19 infections.

Mass testing is already under way for residents, authorities said.

Since the coronavirus pandemic first emerged two years ago in Hubei province's Wuhan, China has used strict local lockdowns, mass testing and contact-tracing apps to try and eliminate outbreaks as soon as cases are detected, sparing the country the mass deaths witnessed around the rest of the world.

Millions were confined to their homes in multiple Chinese cities in the run-up to the Olympics after cases involving both the Delta and Omicron coronavirus variants flared. The outbreaks were mostly stamped out.

In December, 13 million residents of the northern megacity of Xi'an were placed under strict home confinement for over a month after an outbreak of more than 2,000 cases.

Residents complained of grocery shortages and overly harsh enforcement of lockdown measures by local officials, which saw patients blocked from receiving critical medical treatment, leading to deaths in some cases.

China reported 79 new cases nationwide Monday, of which 37 were in Guangxi.

Meanwhile, Hong Kong's zero-Covid policy is on the ropes after a record number of new infections was announced over the weekend, sending officials scrambling to ramp up testing capacity and warning that a tightening of virus-control measures could be needed.

China's borders with the rest of the world, including Hong Kong, are largely sealed.

Covid-positive PNG PM returns from Beijing Olympics
Port Moresby (AFP) Feb 7, 2022 –

Papua New Guinea's prime minister has returned home from Beijing after a positive Covid-19 diagnosis scuppered plans for face-to-face meetings with Chinese leaders, the government said.

James Marape was in China to attend the opening ceremony of the Winter Olympics but "returned a positive test result upon arrival in Beijing last Thursday evening," the government said in a statement on Sunday.

Marape had been expected to meet Chinese President Xi Jinping but instead held a "virtual meeting" with premier Li Keqiang.

The Papua New Guinea leader's trip to France for this week's "One Ocean Summit" hosted by President Emmanuel Macron has been abandoned, officials said.

Papua New Guinea has officially recorded 37,390 Covid cases in a country of nine million people.

But testing and tracing are minimal, and the real number is believed to be in the millions. Under four percent of the population is vaccinated.

Clinics around the country reported at least 2.6 million people — more than a quarter of the population — presented with flu or pneumonia-like symptoms between March 2020 and September 2021.

Marape's visit to Beijing had been hailed as another deepening of ties, as China vies with the United States for influence in the South Pacific region.

His condition is not known as he was ushered quickly through the airport on Sunday with close contacts prohibited. Marape is now in isolation.