Riot police have broken up an unauthorized protest in Casablanca by several hundred people, including many supporters of Morocco's best-known Islamist movement.
The state-run MAP news agency says members of the banned Islamist group, the Justice and Spirituality movement, gathered on a Casablanca square and "tried to start their march with violence" on Sunday.
An Interior Ministry official told The Associated Press that about 50 protesters were arrested and four officers injured.
A movement spokesman couldn't be immediately reached for comment via mobile phone.
King Mohammed VI said Wednesday that Morocco will revise its constitution for the first time in 15 years _ part of steps to build greater democracy amid a push for it across the Arab world.