US Secretary of State Mike Pompeo said Monday he is "deeply troubled" by the Hong Kong arrest of pro-democracy media mogul Jimmy Lai, accusing Beijing of an assault on rights and freedoms in the territory.

"I'm deeply troubled by reports of the arrest of @JimmyLaiApple under Hong Kong's draconian National Security Law," Pompeo tweeted, calling it "further proof that the CCP (Chinese Communist Party) has eviscerated Hong Kong's freedoms and eroded the rights of its people."

Lai's Monday arrest was part of a sweeping crackdown on dissent since China imposed a security law on the city, and sparked a fresh round of condemnation over Hong Kong's stuttering freedoms.