Serbian President Aleksandar Vucic announced tougher measures against anti-government protesters after days of violent clashes across the country.

Despite his threats, thousands demonstrated Sunday in Belgrade and other towns, demanding the release of detained protesters.

Vucic denounced the unrest as “terrorism” allegedly orchestrated by the West, though without evidence, and warned of harsher state action within a week.

The unrest, which has seen offices of Vucic’s ruling party set on fire and police accused of excessive force, follows nine months of protests sparked by a deadly infrastructure collapse blamed on corruption, the Associated Press has reported.

Vucic, criticized for eroding democratic freedoms, has leaned on support from Russia and China while pursuing EU membership.