A lawyer acting for democracy campaigners was among the people arrested today in the biggest crackdown yet under the region's new national security law, according to local press reports. The arrests of more than 50 opposition figures were condemned by the UK foreign secretary. 

In an operation involving more than 1,000 officers, police raided Hong Kong firm Ho Tse Wai & Partners and arrested John Clancey, a partner and a US citizen, the South China Morning Post reports. He is the first American to be arrested under the National Security Law imposed on Hong Kong last year. 

Meanwhile, China said it would revoke the licences of two mainland China lawyers acting in the case of 12 Hong Kong residents accused of trying to flee to Taiwan, the Independent reports. A court in Shenzhen last week sentenced 10 of the 12 to prison terms while two were returned to Hong Kong for trial on charges related to anti-government protests.  

In a statement this afternoon, Dominic Raab, the foreign secretary, said: 'The mass arrest of politicians and activists in Hong Kong is a grievous attack on Hong Kong’s rights and freedoms. These arrests demonstrate that the Hong Kong and Chinese authorities deliberately misled the world about the true purpose of the National Security Law, which is being used to crush dissent and opposing political views.'