The arrest of journalists in Hong Kong has showed that Beijing’s national security law was being used to suppress opposition, Downing Street has said.

ITV News said it is seeking answers from authorities in Hong Kong after its freelancer Wilson Li was arrested under the city’s new national security law.

The broadcaster on Monday said Mr Li was one of nine people arrested by the Hong Kong Police on suspicion of breaching the law.

Hong Kong media tycoon tycoon Jimmy Lai was also arrested on suspicion of collusion with foreign powers, his aid said, in the highest-profile use yet of the city’s new national security law.

The Prime Minister’s spokesman said the Government was “deeply concerned” over the arrest of Mr Lai and the others.

He added: “Freedom of the press is explicitly guaranteed in the Sino-British joint declaration and basic law and is supposed to be protected under article four of the national security law.

“This is further evidence that the national security law is being used as a pretext to silence opposition.

“The Hong Kong authorities must uphold the rights and the freedoms of its people.”

The national security law came into effect on June 30 and has been criticised as a means to curb dissent after anti-government protests rocked Hong Kong last year.

The security law outlaws secessionist, subversive and terrorist acts, as well as collusion with foreign forces in the city’s internal affairs.

The maximum punishment for serious offenders is life imprisonment.

Hong Kong police said nine people aged between 23 and 72 had been arrested on suspicion of violating the national security law.

It said that offences included “collusion with a foreign country/external elements to endanger national security”.

An ITV News spokeswoman said: “We can confirm that Wilson Li works for ITV News in a freelance capacity.

“We are concerned to hear of his arrest and are urgently seeking clarification on the circumstances.”

Mr Lai, masked and wearing a blue shirt and a light grey blazer, was led out of his mansion in Kowloon by police officers also wearing surgical masks and was taken away.

“Jimmy Lai is being arrested for collusion with foreign powers at this time,” his aide Mark Simon wrote on Twitter.

Mr Simon said that police searched both Mr Lai and his son’s home, as well as other members of media group Next Digital, which Mr Lai founded.

More than a hundred police also raided Next Digital’s headquarters in Hong Kong, entering the newsroom and searching the desks.

Next Digital operates the Apple Daily tabloid, which Mr Lai founded in 1995, ahead of Britain’s handover of Hong Kong to China.