Six people have been injured in clashes between opponents and supporters of Venezuela's President Hugo Chavez.
The violence is the worst Caracas has seen for several months
The fighting broke out as opponents marched in the capital Caracas to demand electoral reform ahead of December's parliamentary elections.
Bottles, rocks, fireworks and tear gas were thrown in the worst violence between the two sides for months.
Venezuela has been relatively calm since President Chavez won a referendum on his rule in August 2004.
But his opponents claim the vote was tainted by fraud, and believe the national electoral board is made up of his supporters - charges the board deny.
Hundreds of people marched on the capital on Saturday to call for officials on the National Election Council to be replaced before December's poll.
They marched towards the National Assembly in downtown Caracas chanting anti-Chavez slogans and waving Venezuelan flags.
One man's banner read: "We need a New National Elections Council, Now!"
But as they neared the city centre skirmishes broke out with supporters of the president.
"A woman hit me hard in the head from behind with a stick," said 50-year-old opposition supporter Marisela Riera.
"The metropolitan police were beside me and did nothing."
The wounded were whisked away by emergency crews on motorbikes, Reuters news agency reported.