Former Hong Kong lawmaker and pro-independence activist Sixtus Leung said Friday he had left the city and was in the United States to seek asylum.

He is the latest in a string of democracy activists and former legislators who have fled Hong Kong since Beijing imposed a sweeping national security law on the city in June.

"I, Sixtus 'Baggio' Leung... hereby declare the severance of all ties with my family in Hong Kong," the 34 year-old said in a Facebook post.

Haven Assistance, an overseas democracy group found by Hong Kong activists in exile, said Leung had left Hong Kong on November 30, arrived in the US the next day and decided to "seek asylum in the US amid profound political persecution".

"Because of his political views, Mr. Leung said he was first illegitimately deprived of his representation and voting rights, and subsequent retaliation and suppression followed," Haven Assistance said in a statement.

Leung had called for the semi-autonomous city to split from China as its freedoms came under threat from Beijing.

He and a fellow activist were jailed for four weeks for unlawful assembly and attempted forcible entry after trying to barge into a Legislative Council meeting in 2016.

Despite being elected, the pair were never allowed to take up their seats after protesting at their swearing-in ceremony by misreading their oaths of office and draping themselves in "Hong Kong is not China" flags in the same year.

Former Hong Kong lawmaker Sixtus Leung (pictured with hand raised during a protest at the Legislative Council in 2016) says he is seeking asylum in the United States Former Hong Kong lawmaker Sixtus Leung (pictured with hand raised during a protest at the Legislative Council in 2016) says he is seeking asylum in the United States Photo: AFP / ANTHONY WALLACE

Leung was declared bankrupt by a court as the city's legislature requested the return of his salary and funds paid to him following his disqualification.

After last year's massive democracy protests, Beijing imposed a broadly-worded security law that outlaws certain political views.

Two dozen people have been arrested under the legislation and four have so far been officially charged by the police.

They include pro-democracy media tycoon Jimmy Lai, who was charged Friday, accused of colluding with foreign forces, and will appear in court on Saturday morning.

Leung said he had resigned from his position and duties at the pro-independence political party Youngspiration and that his views and actions were not linked to his family, relatives and friends.

On Monday, police froze bank accounts of fugitive former lawmaker Ted Hui and his family members after he fled overseas earlier this month.

The veteran opposition activist is facing a string of prosecutions linked to his pro-democracy protests.