Police in Zimbabwe's capital, Harare, have used tear gas and water cannons to break up a protest by minibus drivers.

The unrest began when drivers erected barricades in a protest against harassment and roadblocks by police demanding bribes.

When security forced stepped in, some local residents joined the protesters and threw stones at police.

Some demonstrators are reported to have been beaten up. Thirty people have been arrested.

Zimbabwe has become increasing volatile in recent weeks with frequent protests against economic hardship and alleged government corruption.

Police say they have reduced the number of roadblocks following complaints.

The economy has struggled since a government programme seized most white-owned farms in 2000, causing exports to tumble.

Robert Mugabe, 92, has been in power since independence in 1980.

Critics accuse him of using violence and rigging during recent elections - allegations he denies.

Official statistics say most citizens live on just one dollar a day.