US Secretary of State Mike Pompeo on Saturday criticized the arrests of several high-profile democracy campaigners in Hong Kong, saying they were “deeply concerning.”

Earlier in the day, police in the Asian financial hub rounded up 15 activists on charges related to massive demonstrations that rocked the city last year.

“Arrests of pro-democracy activists in Hong Kong are deeply concerning — politicized law enforcement is inconsistent with universal values of freedom of expression, association, and peaceful assembly,” Pompeo said in a tweet.