Hong Kong police are investigating a campus protest over suspected violations of a security law imposed by China’s central government, fueling growing concerns about curbs on freedom of expression in the Asian financial center.

The Hong Kong Police Force’s newly established national security department has begun probing reports that protesters advocated for independence from China during a demonstration Thursday at the Chinese University of Hong Kong (CUHK), the police said in a statement. Protesters "displayed banners and flags, as well as chanted slogans advocating ‘Hong Kong independence,’” and vandalized the campus with spray paint, the police said.

"Police attach great importance to and severely condemn the blatant violation of the National Security Law and criminal damages at the campus,” the police said.