As many as 20 people remain missing following violent protests in Indonesia, initially sparked by outrage over lawmakers' lavish perks and now fueled by anger toward police, a rights group said Tuesday.

At least six people have been killed since protests rocked Southeast Asia's biggest economy last week, intensified by spreading footage of the killing of a young delivery driver by a paramilitary police unit.

The unrest emerged in cities across Indonesia, forcing President Prabowo Subianto into a U-turn on lawmaker perks after the worst protests since the ex-general took power last year.

The Jakarta-based Commission for the Disappeared and Victims of Violence (KontraS) said 23 reports of missing persons had been received by Monday.

"After the search and verification process, 20 missing persons remain unfound," it said in a statement.