Hong Kong is one of the most densely populated cities in the world

Hong Kong's government has ordered the compulsory testing of all of its 7.5 million citizens as the city battles surging coronavirus infections.

Chief Executive Carrie Lam said residents would have to undergo three rounds of tests starting in mid-March.

Schools will break early for summer.

The territory is trying to adhere to China's "zero Covid" policy, but the highly contagious Omicron variant has overwhelmed its hospitals and testing and quarantine facilities.

While other parts of the world are learning to live with the disease, China's policy is to try to eradicate infection through early testing, detailed contact tracing and strict quarantine and travel restrictions.

"The coming one to three months are crucial in fighting the pandemic," Ms Lam told reporters. "This quickly worsening epidemic has far exceeded the Hong Kong government's ability to tackle it."

All residents will have to undergo three rounds of PCR testing, at intervals of about a week. Ms Lam did not set a date for testing to start but said capacity would be increased to a million daily tests.

"Since we have a population of some seven million people, testing will take about seven days."

In between compulsory tests residents will be required to conduct daily rapid antigen testing. Experts have warned that huge numbers of the population could be in isolation within weeks.

Entire cities have been locked down in China, but such a move was not being considered in Hong Kong because it was "not realistic", Ms Lam said.

It's the first time everyone in the special administrative region will have been tested - a policy enacted elsewhere in China.

The former British colony reported 6,211 new cases on Tuesday, but the actual figure is thought to be much higher because of a backlog in testing.

Hong Kong, which had been hailed for its pandemic control over the past two years, has seen an exponential rise in infections since Omicron laid bare its defences.

In the first two years of the pandemic the territory recorded only 12,650 cases and just over 200 deaths, numbers far below most other similar-sized cities. The total number of cases has multiplied five-fold since January.

Modelling by the University of Hong Kong (HKU) shows Hong Kong's total deaths from coronavirus could top 3,200 by mid-May, with infections peaking at 180,000 a day, far higher than earlier forecasts.

Tens of thousands of new isolation spaces are being created for those who test positive, but Ms Lam conceded the new measures may not succeed.

There is rising fatigue among Hong Kong residents who have had to endure tight measures that include the closure of most public venues like pubs, gyms and churches, and severe travel restrictions.

The government has also struggled to persuade residents to get vaccinated, with a relatively low uptake among the elderly in particular.