Opposition parties are demanding electoral reform and free elections clashed with police at an anti-government rally in Sanaa
Police have fired warning shots and hurled batons at an opposition rally in the Yemeni capital of Sanaa.
Early reports suggest at least five protestors and two police officers were injured in the clashes.
Thousands gathered for the rally called by Common Forum, an opposition umbrella group demanding electoral reform anbd free and fair elections.
The grouping is threatening to boycott of next year's parliamentary poll unless its demands are met.
The party of President Ali Abdullah Saleh, the General People's Congress, has refused election monitors or to reform the electoral law.
The Yemeni Socialist party and the Islamist al-Islah (Reform) Party want government officials banned from using their power to influence the vote and an end to voter-registration in the workplace.
On Monday, parliament postponed local elections for another four years, citing expense and the fact that the last local elections were only held in September 2006.
This prompted a parliamentary walk-out by opposition parties.
President Saleh has ruled the middle east's poorest state since its unification in 1990. He was re-elected in 2006.