China's largest city of Shanghai has ordered mass testing on all 1.3 million residents of its downtown Yangpu district, confining them to their homes at least until results are known.

The demand was an echo of measures ordered over the summer which led to a two-month lockdown of the entire city of 25 million.

The previous lockdown devastated the local economy, prompting food shortages and rare confrontations between residents and the authorities.

Authorities said restrictions would last just days but then kept extending the deadline.

China has shown no sign of backing away from its hard-line "zero-COVID" policy since a major congress of the ruling Communist Party that concluded this week by awarding President Xi Jinping a third five-year term in power and packed top bodies with his loyalists.

Strict measures have been imposed across the country, from Shanghai in the east to Tibet far to the west, where anti-lockdown protests have also been reported.

Mobile phone footage smuggled out of the region showed crowds of both native Tibetans and Han Chinese migrants milling in the streets of Lhasa to protest a lockdown lasting more than 70 days.

The footage was reportedly shot on Wednesday night but there was no sign of violence.

Lhasa has been under tight surveillance since bloody anti-government protests broke out in the city in 2008 before spreading across Tibetan areas.

Signs tough COVID measures will continue

Despite public anger the former chairman of Shanghai's Communist Party Committee, the city's top official who was ultimately responsible for the lockdown measures, was given the second highest spot in the party's all-powerful Politburo Standing Committee.

Li Qiang, who had been Mr Xi's virtual chief-of-staff while he headed the eastern province of Zhejiang, was replaced by Beijing Mayor Chen Jining, a former president of Beijing's prestigious Tsinghua University and minister of environmental protection.

Mr Chen, 58, was educated at Brunel University London and worked at Imperial College London, where he earned a PhD degree in civil and environmental engineering in 1993.

Many Chinese had hoped for a relaxation of the strict COVID-19 protocols, which remain in place even while the rest of the world has opened up.

China's borders have remained largely closed and arrivals must undergo a 10-day quarantine at a designated space.

Despite its costs, and the World Health Organization calling it unsustainable, China has credited the strategy with keeping case numbers and deaths at a fraction of those in other countries, although Beijing's figures have frequently been questioned.

China on Friday reported 1,337 new cases — most of them asymptomatic — and no new deaths.

Shanghai reported 11 asymptomatic cases and Tibet had one confirmed case with symptoms and five asymptomatic cases.

China has recorded a total of 258,660 cases and 5,226 deaths since the pandemic was first detected in the central city of Wuhan in late 2019.

In a sign China's tough measures will be maintained in the long term, Shanghai plans to build a permanent quarantine centre on an island in the Huangpu River that divides the financial hub, according to the business magazine Caixin.

The 1.6-billion-yuan ($343.98 million) project on Fuxing Island will expand existing facilities to create 3,009 isolation rooms and 3,250 beds, with construction expected to be completed in six months, Caixin said.

COVID booster levels low

China's domestically developed vaccines are considered relatively ineffective, and it has refused to approve foreign brands such as Pfizer, Moderna, AstraZeneca and Johnson & Johnson.

Still, China wanted more people to get booster shots before it relaxed its restrictions.

As of mid-October, 90 per cent of Chinese were fully vaccinated and 57 per cent had received a booster shot.