Montenegrin police have fired tear gas against stone-hurling opposition protesters demanding government's resignation and an early election in the small Balkan state.

Several thousand opposition supporters gathered Sunday evening in downtown Podgorica. Police officers fired tear gas when they threw stones at them. A similar protest was held in the capital on Saturday when police also intervened.

Anti-government leaders had staged daily protests in a main street in Podgorica, but police removed their tents on Saturday. Opposition parties have vowed to repeatedly gather in a bid to force an early election.

The opposition groups earlier last week also staged an anti-NATO protest during a visit by alliance Secretary-General Jens Stoltenberg to Montenegro.

Opponents have accused Montenegro's government of authoritarian rule and using pressure against opponents.