Joshua Wong, a prominent Hong Kong pro-democracy activist, was arrested on Thursday for "participating in an unauthorized assembly" last October, according to a post on his Twitter account.

"Joshua is arrested when reporting to Central Police Station at about 1 p.m. today. The arrest is related to participating in an unauthorized assembly on 5 Oct last year. He is told to have violated the draconian anti-mask law as well," the post read.

Hong Kong's anti-mask law, which came into effect on October 5, 2019, bans people from covering their faces during protests.

"Today's arrest is a notorious abuse to the criminal justice system by placing charges ruled unconstitutional earlier. However, I choose not to surrender.

"Facing max. The penalty of 5 years in jail for unauthorized assembly and 1yr for wearing a mask, I'm not deterred whenever I think of fellow protesters who are struggling in detention in Hong Kong or in mainland China," it added.

According to a report in the South China Morning Post, another activist, Koo Sze-yiu was also detained in connection with the October 2019 protest.

The police has confirmed that two people were arrested on Thursday after they were accused of "knowingly taking part in an unauthorised assembly".

The two activists are expected to appear in court on September 30.

Last month, Wong was also charged for participating in a banned vigil marking the anniversary of the 1989 Tiananmen Square crackdown in China.

Despite the ban imposed in the wake of the Covid-19 pandemic, thousands attended the June 4 vigil to mourn those who died in the crackdown 31 years ago..