A Hong Kong pro-independence activist who was jailed under a sweeping Chinese national security law has fled to the UK to seek political asylum, according to his social media posts.

Tony Chung was among the first to be convicted under the Beijing-imposed law that was introduced after the 2019 pro-democracy protests.

He was found guilty of secession and money laundering in 2020 and sentenced to 43 months in prison.

In two Instagram posts on Friday, Mr Chung detailed how authorities closely watched him after he was released from prison.

He said he was asked to meet regularly with national security authorities and report to them on where he had been, whom he had met with as well as his conversations. He also claimed authorities offered to pay him to inform on others to prove he had reformed himself.

They also proposed he should go to mainland China.

Mr Chung said he was made to sign a document that barred him from disclosing his conversations with the authorities, so he could not seek help from any lawyers nor tell anyone about his situation.

“Under enormous stress and fear, I can only endure silently,” he said.

The intimidation faced by Hong Kong dissidents like Mr Chung reflects the drastic erosion of the freedoms promised to the former British colony when it returned to China in 1997.

But both the Beijing and Hong Kong governments have hailed the security law for bringing stability to the city.

Hong Kong police have offered rewards for information leading to the arrests of 13 overseas-based activities and drew criticism from Western governments.

Earlier in December, prominent pro-democracy activist Agnes Chow, who left Hong Kong for Canada and does not plan to return to fulfil her bail conditions, reported similar pressure from authorities.

Her passport, confiscated earlier by police, was only returned to her upon meeting certain conditions, including a visit to mainland China with authorities, she said.

In an email reply to the Associated Press, Hong Kong police said Ms Chow failed to show up at a police station on Thursday as required and violated her bail terms, pledging they would “spare no effort in bringing her to justice”.

They strongly condemned the breach of supervision orders or bail conditions by individuals who have fled the city.

“Not only have they failed to reflect on the harms they have caused to Hong Kong and members of the public, but they have also shamefully begged for assistance from foreign anti-China forces under the guise of being victims,” the police said.

They did not confirm Mr Chung’s claims that they had offered to pay him informant fees but said the national security department has been effectively collecting intelligence through various channels and individuals.

Local media, including the South China Morning Post, quoted unnamed sources saying that her parents went to a police station to assist their investigation on Friday.

Mr Chung was convener of the now-dissolved pro-independence student organisation Studentlocalism before being arrested in 2020 near the United States consulate in Hong Kong, where media reports said he was hoping to seek protection.

According to his Instagram posts, Mr Chung was under a supervision order by the city’s Correctional Services Department for a year after his release from prison, and was banned from speaking publicly.

In September, he said national security authorities asked him to take a trip to mainland China, but he told them he was unwilling to do so. The authorities then asked him if he was being reluctant because he was still involved in activities endangering national security.

Mr Chung said he started feeling sick from time to time since October. Western and Chinese doctors told him that his immune system weakened because he was under huge mental stress.

He later persuaded correctional services authorities to let him travel to Okinawa, Japan, for a holiday to manage his emotions. During the trip, he sought help from organisations and people based overseas.

He arrived in Britain from Japan on Wednesday to seek asylum.

“This also means I can no longer return to my home, Hong Kong, in foreseeable future,” he said.

“Although I had anticipated the arrival of this day in the past, I had a heavy heart when I made up my mind.”

In the future, Mr Chung said he would devote himself for his city as a “Hongkonger in exile”.

“I believe only when Hong Kong people don’t give up, the seeds of freedom and democracy will sprout again one day,” he said.