CAIRO — Egypt’s Interior Minister vowed Saturday to investigate the beating of a naked man by riot police that threatened to further inflame popular anger against security forces, but suggested that initial results absolve the police of direct abuse.

The beating was caught on camera and broadcast live on television late Friday. Video showed police trying to bundle the naked man into a police van after beating him.

Less than 24 hours after the incident, several thousand anti-government demonstrators marched again on the palace Saturday denouncing the police and Islamist President Mohammed Morsi after a week of violent protests that claimed more than 60 lives nationwide.