Hong Kong, Aug 13 (IANS): Hong Kong tycoon Jimmy Lai - the most high-profile person to be detained under a controversial new security law - has warned young protesters they need to be "more cautious" now.

Lai was arrested on Monday, and his newspaper offices raided by hundreds of police, in scenes that shocked many.

Speaking after his release on bail, Lai told the BBC he believed his arrest was "just the beginning".

There will be "a long fight" ahead for Hong Kong's freedoms, he added.

Lai, who has been a prominent pro-democracy voice and a supporter of protests that erupted last year, owns Apple Daily, one of Hong Kong's most-read newspapers.

He and nine other activists were detained on Monday over allegations including collusion with foreign forces, under a national security law imposed by China in June.

The sweep of arrests has raised fears that China will use the new law to undertake a broad crackdown on Hong Kong's pro-democracy activists and media figures.

Speaking to Newshour on the BBC World Service, Lai said he was surprised when he saw police arrive at his home on Monday morning.

While he had been arrested before, this was "more scary" because it came under the national security law imposed by China, he said.

Both his sons were also arrested on "bogus charges", he said, although he added that he had no regrets about his pro-democracy activism.

"When I was in custody I could not sleep... I was thinking, if I knew that was going to happen to me now, [with] even more hardship [on the way], would I have done the same thing?

"I would not have [done things] another way - this is my character," he added.

However, he warned protesters that they would now have to be "more cautious in our resistance to preserve our rule of law and freedom", as the sweeping new security law made the environment more dangerous for activists.

"We have to be more careful and creative in [our] resistance... we can't be as radical as before - especially young people - because the more radical [we are] the shorter lifespan we have in our fighting.

"We have to really use our brain and patience, because this is a long fight."

Lai's arrest has been welcomed by Chinese state media, who have described him as a "riot supporter" and his publications as having been "instigating hatred, spreading rumours and smearing Hong Kong authorities and the mainland for years".