HONG KONG (Reuters) - Hundreds of Hong Kong anti-government activists gathered outside a detention centre on Friday, demanding the release of arrested activists and denouncing a police crackdown on a fund-raising platform supporting protesters in need.

Hong Kong protesters gather outside a detention center in Lai Chi Kok to demand the release of protesters, in Hong Kong, China, December 20, 2019. REUTERS/Lucy Nicholson

Congregating outside a detention centre in the western Kowloon district of Lai Chi Kok, the crowds held up signs with the words “In Solidarity We Stand”, waved flags and demanded the release of all protesters.

“I feel quite sad for the young people, they are fighting for liberty...for us all,” said Ben, a 68-year-old retiree.

After a relative lull in sometimes violent protests that have gripped the former British colony over the past six months, some protesters were alarmed by police moves to freeze HK$70 million (6.91 million pounds) in bank deposits held by fund-raiser Spark Alliance.

The protesters are angry at perceived Chinese meddling in the city’s freedoms guaranteed under the “one country, two systems” formula when it returned to Chinese rule in 1997. China denies the charge.

Police said one man fired a pistol at them in the New Territories town of Tai Po, but did not say if it was protest related. They seized a “pistol-like object” and detained one man.

The use of firearms in Hong Kong is very rare, even by police.

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Spark Alliance was launched in 2016 to support protesters on a number of fronts including legal fees. Police said they arrested three men and one woman for suspected “money laundering”, according to a statement.

Spark Alliance on its Facebook page said it “condemned such smear tactics” by the police.

Pro-democracy lawmaker Claudia Mo, who was also at the protest, said the police case was tenuous at best, and she questioned why the fund had run for several years without incident.

“It’s too convenient for the authorities to call it money laundering,” she said.

Global banking group HSBC on Friday strongly denied any link between the police clampdown on Spark Alliance and the earlier closure of an HSBC bank account tied to the group.

A small group of protesters had earlier called for a boycott of the bank at its headquarters in the heart of Hong Kong’s financial district.

“Our decision (to close the account) is completely unrelated to the Hong Kong police’s arrest of the four individuals on 19 December 2019,” HSBC said in a statement.

“We closed the account in November 2019 following direct instruction from the customer.”

Hong Kong has been convulsed by anti-government, pro-democracy protests in the city’s worst political crisis in decades.

They have also posed a grave populist challenge to Chinese leader Xi Jinping who just completed an official visit to the neighbouring gambling hub of Macau, which celebrated the 20th anniversary of its handover from Portuguese to Chinese rule.

Amid a rising tide of anti-China sentiment, as public anger flares towards China’s perceived squeeze on the city’s freedoms, some mainland Chinese banks and businesses have been vandalised.