Recently, however, supporters have been handing him cash.

“They don’t want to leave any record,” said Lee, whose group is best known for organising the annual June 4 candlelight vigil in Victoria Park to remember Beijing’s Tiananmen Square crackdown of 1989.

Donations to activist organisations, opposition parties and those supporting anti-government protesters have come into the spotlight, following recent cases in which police cited money-laundering laws in targeting individuals and groups.

The cases have raised questions about whether crowdfunding is still allowed for opposition parties and groups that support anti-government activities, especially in light of the national security law imposed by Beijing on Hong Kong in June.

The first case arose a year ago, when police arrested four men and froze HK$70 million raised by Spark Alliance, a group that supported Hong Kong anti-government protesters.

This month, money-laundering allegations were directed at former opposition lawmaker Ted Hui Chi-fung, who has fled Hong Kong, and the Good Neighbour North District Church, a Christian group which helped protesters.

Soon after leaving with his family for Britain via Denmark earlier this month, Hui found that his bank accounts, as well as those of his wife and parents, were blocked.

Police, who confirmed freezing HK$850,000 of his assets, accused him of embezzlement and breaching the national security law.

Hui said he raised HK$3.5 million to initiate private legal action against a police officer and a taxi driver accused of deliberately ploughing into a crowd of protesters last year, but the money was in an account under a law firm and had nothing to do with his account and those of his family members.

The church, whose “Protect the Children” ministry supported young activists during last year’s protests, called the police action “political retaliation”.

At least three of its bank accounts were frozen, including those of its pastor and his wife. Police said an ongoing investigation into money laundering and fraud found the church received HK$27 million in donations over more than a year but publicly declared less than a third.

Last month, teacher Yeung Pok-man, 30, was arrested on suspicion of money laundering over HK$5.8 million he raised in a crowdfunding campaign for his ailing parents. Police said the sum far exceeded his HK$500,000 target.

Yeung was also connected to the protests. He was sentenced to nine weeks’ jail in September last year for kicking a police officer during an anti-government protest. He was arrested for money laundering while on bail pending his appeal.

Last month too, Wan Yiu-sing, an online radio host known for his on-air moniker “Giggs”, was arrested with his wife for money laundering in connection with a crowdfunding drive to support protesters who fled to Taiwan. Wan and his assistant were also arrested and accused of aiding secessionist activity, which is banned under the national security law.

On Thursday, Secretary for Security John Lee Ka-chiu defended the police action, saying the force had acted in accordance with anti-money-laundering legislation.