Pro-democracy activist Isaac Cheng Ka-long has left Hong Kong for Taiwan, sources said, sparking speculation he could be on the run.

The 21-year-old Cheng, former vice-chairman of the now-disbanded Demosisto, is on bail after Customs officers arrested him last May for false product descriptions for masks.

Demosisto sold masks in boxes stating they were "not made in China," but could not provide certification to back these claims, Customs had said.

Under his bail conditions, he is allowed to leave Hong Kong. Cheng did not respond to The Standard before editorial deadline.

The party was disbanded before the implementation of the national security law last June. The former chairman of the party, Nathan Law Kwun-chung, left Hong Kong for the United Kingdom in a self-imposed exile last year. He has since been put on the wanted list for national security offenses.

Two other party executives, secretary general Joshua Wong Chi-fung and standing committee member Agnes Chow Ting, were jailed for illegal assembly over a 2019 demonstration outside Wan Chai police headquarters.

News of Cheng being on the run came hours after exiled former lawmaker Ted Hui Chi-fung posted on Facebook that he had arrived in Australia yesterday after staying in Britain for three months. He added that he has no plans to apply for political asylum yet.

In the Facebook post, Hui wrote that he had chosen Australia because he had more relatives and there are fewer exiled Hong Kong politicians in the country.

Hui, 38, said he met Law a few times and learned about his work and plans while he was in Britain.

"As both Nathan and I have a similar role in Britain, we should spread out across more continents, covering every corner in the world," Hui said.

"We will have better work distribution in international lobbying and assisting organizations that help Hong Kong people."

A team of exiled Hongkongers is lobbying in Britain and Europe, but there are relatively few such people in Australia and New Zealand, which have had conflicts with Beijing over democracy and freedoms, he added.

Hui also said he entered Australia with a tourist visa, but added that applying for political asylum will be the last resort.

Pro-establishment former district councilor Chan Wan-sang slammed Hui for "smearing China and Hong Kong" in different countries and said Hui is only going to Australia out of personal considerations, as it is cheaper to live there than in the UK.

Chan also said Australian authorities allowing Hui to enter the country might be a move to achieve their political goals, as Australia, which is a part of the Five Eyes alliance, has opposed the national security law in Hong Kong.

Last November, Hui claimed that he was going to Denmark for a work trip while out on bail. Three days after arriving in Denmark, Hui declared he was in exile.

Issac Cheng is said to have fled to Taiwan.

Ted Hui

Activist on bail flies to Taiwan