Hong Kong (dpa) - Some 50 pro-democratic activists and former lawmakers have been arrested in Hong Kong for alleged violations of the city's new national security law, local media reported on Wednesday.

"They were arrested on suspicion of subversion," the South China Morning Post (SCMP) cited a police source as saying.

According to the paper, activists and former lawmakers were arrested on Wednesday morning over their roles in a primary run-off vote ahead of Legislative Council (LegCo) elections which were due to be held in September.

Among those detained were former lawmakers Lam Cheuk-ting, Andrew Wan and Alvin Yeung as well as activist Benny Tai, one of the leaders of Hong Kong's 2014 Umbrella Movement, the SCMP reported.

The apartment of prominent activist Joshua Wong, who is currently in jail for inciting and organizing an unauthorized assembly, was also searched.

On July 11 and 12 a record 610,000 Hong Kongers voted in the primary elections for the pro-Democratic camp.

The goal of the "Democrat Camp 35+ Primary Election" was to gain a majority of 35 or more seats (more than half) in the September election, a move which would give them more power to veto pro-establishment legislation.

The government said the primaries were "illegal" and disqualified 12 candidates from running, including Wong, before Chief Executive Carrie Lam postponed the elections for a year citing a surge in Covid-19 cases.

The SCMP said this was the largest mass arrest under the highly controversial national security law, which was imposed in the territory by Beijing in June ushering in a crackdown on the territory's democratic opposition.

In December, a 19-year-old man was sentenced to four months in prison for allegedly desecrating the Chinese flag. Another 10 Hong Kong residents were also sentenced to between seven months and three years in prison in the southern Chinese city of Shenzhen for trying to flee to Taiwan.

Beijing's enactment of the new law has led to a swift crackdown on democratic freedoms in the previously semi-autonomous city, drawing international criticism. The law targets secession, subversion, terrorism and collusion with foreign forces in the financial hub.

Taiwan's ruling Democratic Progressive Party (DPP) on Wednesday condemned the arrests, calling on Beijing to stop reinforcing the "evil law" in Hong Kong.

"DPP is deeply concerned about the future of Hong Kong and feel angry about what the Chinese authorities have done," the party said in a statement, vowing to keep pushing the Taiwan government to further assist Hong Kong.