Hong Kong police made the highest-profile arrest yet under China's new national security law for the city on Monday (August 10)
That's according to the top aide of media tycoon Jimmy Lai, who he says was taken in on suspicion of collusion with foreign forces.
Lai has been one of the most prominent democracy activists in the Chinese-ruled city.
His company Next Media publishes the local tabloid, Apple Daily.
Lai's also been an ardent critic of Beijing, which imposed the sweeping new law at the end of June.
The new law was condemned by Western countries.
It punishes with up to life in prison anything China considers subversion, secession, terrorism - or collusion with foreign forces.
Critics say it crushes freedoms in Hong Kong, while supporters say it will bring stability after last year's prolonged pro-democracy protests.
On Monday morning the city's police said they had arrested seven people on suspicion of breaching the city's new national security law.
They cited offences including collusion with foreign powers, and said the arrested were all local men, aged 39-72, without naming them.
Police said the operation was ongoing and further arrests were possible.
On major cases in Hong Kong, the central government in Beijing can claim jurisdiction.
The new law allows agents to take suspects across the border for trials in Communist Party-controlled courts.