Hong Kong's prisons on Friday reported a worsening coronavirus outbreak involving more than 200 inmates at a time when hundreds of political activists and protesters are behind bars.

The city is in the throes of its worst-ever Covid-19 wave, registering thousands of cases every day that are overwhelming hospitals and government efforts to isolate infected people.

The outbreak -- fuelled by the extremely transmissible Omicron variant -- has also breached the city's prisons, where more than 7,200 people are currently detained.

As of Thursday, there were 202 confirmed infections and 135 preliminary positive prisoners within the system -- a caseload that has grown by more than 20 times in about a week.

"It is anticipated that more cases of infection will be found in the coming week," corrections officials said, adding that clusters had been detected among its staff.

Visits have been suspended since the beginning of February, while one correctional facility has been converted to isolate infected prisoners.

In recent years, newcomers to Hong Kong's prison system have included many of the city's most prominent democracy activists, ensnared in the wake of 2019's massive and at times violent democracy protests.

Beijing stepped in with a sweeping national security law in 2020 to quash dissent.

The bulk of those hit with the law have been awaiting trial behind bars for months, while others have been convicted of various protest- and speech-related offences.

China has long touted a "zero-Covid" strategy that Hong Kong has adhered to since the start of the pandemic -- keeping infections low with largely closed borders and isolating all patients.

But since Omicron has penetrated those defences, the densely populated city has recorded more than 55,000 cases in 2022 -- compared with just 12,000 in the pandemic's first two years.

More than 250 people have died in the current wave, surpassing the combined toll of all previous pandemic-related deaths.

Caseload 'closer to 200,000'

Hong Kong officials on Friday said there were nearly 22,000 cases reported over the past day, a record high.

The overall number of infected residents, meanwhile, is likely as high as 200,000, former Hospital Authority chief executive Leung Pak-yin has estimated.

Cases could exceed one million -- out of a population of 7.4 million -- by late April, he said Thursday on Facebook.

The European Union's office in Hong Kong and Macau earlier expressed concerns over tough anti-epidemic measures to the government.

"More than 10 percent of EU citizens are leaving Hong Kong due to Covid-related measures and their unpredictability over the year and a half," the office told AFP.

Hong Kong next month will carry out mandatory testing for all city residents, while facilities are currently being built to house the infected.

According to Bloomberg's Covid Resilience Ranking, Hong Kong is now second only to Pakistan as the worst place to live during Covid, down from ninth-best in the world in January 2021.