Witnesses, including local shopkeeper Rachi Zeroual, say several dozen people appeared to have been hurt in Monday's riot. Police say about 10 officers were injured.

Witnesses say police used water canons and tear gas to fight back rioters armed with stones. Many shops were vandalized.

The violence broke out when police acting on a judge's order arrived to raze shacks, some built illegally on a football pitch, in a working-class neighborhood.

Officials plan to tear down a shantytown and build housing in the neighborhood two kilometers (about a mile) from the office of the North African nation's president.