Social activist Lester Shum campaigns in support of Gwyneth Ho (not in picture), a candidate of New Territory East, during a…
Social activist Lester Shum speaks out in Hong Kong, July 11, 2020. Shum and over 50 other pro-democratic activists in Hong Kong reportedly were arrested Jan. 6, 2021, for breaking the city's national security law.

HONG KONG - Over 50 pro-democratic activists in Hong Kong were arrested Wednesday for breaking the city's contentious national security law, local media reported, in the biggest crackdown yet against the democratic opposition under the new law. 

The arrests in the Asian financial hub included well-known democratic figures and former lawmakers James To, Lam Cheuk-ting and Lester Shum, according to the Democratic Party's Facebook page and public broadcaster RTHK. 

Police did not immediately respond to requests for comment. 

The Democratic Party's Facebook page said police arrested the activists for participating in an independently organized ballot last year to select democratic candidates for an upcoming legislature election, which the Hong Kong government and Beijing warned at the time may violate the new law. 

FILE - Pro-democracy lawmaker Lam Cheuk-ting, right, speaks to reporters in Hong Kong, Nov. 12, 2020.

The attempt to win a majority in the 70-seat city legislature, which some candidates said could be used to block government proposals and increase pressure for democratic reforms, was seen as an "act of subversion, in violation of the national security law," the party said. 

The full election for the legislative council has since been postponed, with the government citing the coronavirus. 

The security law was imposed by Beijing on the former British colony in June. 

It punishes what China broadly defines as secession, subversion, terrorism and collusion with foreign forces with up to life in jail. The law has been condemned by the West and human rights groups as a tool to crush dissent in the semi-autonomous, Chinese-ruled city. 

Authorities in Hong Kong and Beijing say it is vital to plug gaping holes in national security defenses exposed by months of sometimes violent anti-government and anti-China protests that rocked the global financial hub in 2019.