Hong Kong, Jul 14 (IANS): One of Hong Kong's most prominent young pro-democracy activists said that he is in London after fleeing the city following the controversial security law imposed by China.

"I boarded my night flight... My destination: London," Nathan Law wrote on Twitter on Monday, a week and a half after saying he had left Hong Kong, the BBC reported.

Law said that he faced "many uncertainties", but had made the decision to leave Hong Kong "in the face of political upheaval".

"We don't even know if our next protest, next court hearing, will be followed by imprisonment," he said, adding that he had put himself in "danger".

"I've kept a low profile on my whereabouts in order to mitigate the risks."

In one post, which appeared to include a aerial photo of London from the window of a passenger plane, he said he had a message for Hong Kongers: "We aren't fractured. On the contrary, we're well-equipped to face the next difficult battle."

Law added that said he had spoken with reporters and was living in a "little apartment".

Law is a one-time student leader who rose to prominence during mass protests in 2014.

He was also a local legislator who co-founded the Demosisto Party with another well-known activist, Joshua Wong.

The party disbanded when China imposed the new law earlier this month.

It is not clear from Law's social media posts on Monday when he arrived in the UK.

Earlier this month, Law told the BBC that he would continue his advocacy work from abroad, and that the people of Hong Kong would not give up their fight.

On July 1, the 27-year-old spoke via video link to a US Congressional hearing on Hong Kong, saying that he was worried about returning to the territory, for fear of being imprisoned by Beijing.

Beijing drafted and passed the legislation last late month that targets acts of secession, subversion, terrorism and collusion with foreign forces, with punishments of up to life in prison for the most serious offences.

It came into effect on July 2.

Under the new rules, Hong Kong police can also raid premises without a court warrant, order internet firms to remove content or seize relevant devices, and demand information from political groups operating outside the city.