The Secretary for Security Chris Tang on Saturday said that the government revoked the passports of six wanted people this month to send a message that there was a high cost to being a fugitive.

Speaking in an interview to mark the second anniversary of the current administration, Tang said fugitives might also lose any foreign travel documents once they were no longer of use to those harbouring them.

"I don't know why these people think that, 'maybe I'll still have the opportunity to travel to other places by using my refugee status as a refugee or another status.' I'm not entirely sure in this regard," Tang said.

"But firstly, you'll not be able to use Hong Kong SAR passports to travel; and secondly, while you may now have value because others sympathise with you - and they have granted you travel documents - you might lose those documents, when you no longer have any value. Then you won't be able to travel."

The six people wanted here for alleged national security offences under homegrown national security legislation include Nathan Law, Mung Siu-tat, Finn Lau, Simon Cheng, Johnny Fok and Tony Choi.

Meanwhile, the security minister also called on Alman Chan, the wanted principal of drug rehabilitation centre Christian Zheng Sheng College, to return to Hong Kong from the UK.

In January, police arrested four directors of the charity which runs the college, on suspicion of conspiracy to defraud. Three others - including Chan, who denies the allegations - were put on the wanted list.

"I noticed that Alman Chan said on social media that 'Oh I did not take any funds from the college and the issue has nothing to do with me, and I'm not involved'.."

"If this is true, I hope he has the courage to return to Hong Kong and explain to us clearly about the whole matter. On the one hand you are running away, and on the other you are making such remarks. This has no meaning."

Separately, Tang said authorities would make sure that the July 1 celebrations pass off peacefully.

Commenting on why there are now fewer protests on July 1, Tang said that, although protesting is allowed, a protest might be hijacked by people with ulterior motives so residents are choosing other options instead.

"I believe Hongkongers, after going through what happened in 2019, they clearly know that - while they want to hold a peaceful protest - many people, who wish to endanger national security or Hong Kong's security, might take the opportunity to conduct acts endangering national security."

Tang said Hong Kong residents know that they might be used, so they have chosen other ways to express their opinions. He also said residents might just feel the government is doing a good job.