Witnesses say riot police have used tear gas and stun grenades to drive back more than 2,000 protesters demanding the release of a jailed opposition leader.

Wednesday's clash outside a Kuwait City prison underscores the rising tensions in the oil-rich Gulf nation between the Western-backed rulers and opposition factions that include Islamists.

The crowd also marched in defiance of orders banning public gatherings of more than 20 people.

Anti-government groups have denounced the detention of former parliament member Musallam al-Barrack for allegedly insulting Kuwait's emir during protests.

The witnesses spoke on condition of anonymity because of fear of reprisals from authorities.

Parliament elections are planned for Dec 1.