On the day the European Union imposed sanctions against Zimbabwe, the national headquarters of the country's main opposition party was attacked by several hundred supporters of President Robert Mugabe's ZANU-PF party.

About 200 young people besieged the Movement for Democratic Change offices in downtown Harare, throwing stones and bricks and calling for the arrest of Morgan Tsvangirai, the party leader.

As the attack got underway, police stood nearby, watching. But after a number of people inside and outside the six-story office building were beaten up, the police moved in and dispersed the mob.

The youths were part of a much larger crowd of more than 6,000 ruling-party demonstrators who marched through the center of the capital. At about the same time as the attack on the MDC headquarters, protesters surrounded the building housing the British embassy, chanting anti-British slogans and denouncing British Prime Minister Tony Blair.

Police stopped the crowd from entering the building. It is not known if any arrests were made.

MDC chief spokesman Learnmore Jongwe called for foreign observers who are in Zimbabwe for next month's presidential election to use their influence to "persuade ZANU-PF to abandon its violent agenda."

Meanwhile, in Bulawayo, Zimbabwe's second city, David Coltart, the chief MDC legal affairs specialist, has been given bail on a charge of firing a weapon in public. Mr. Coltart, who denies the charge, was arrested after he had asked police to disperse a group of youths outside his home whom he said were members of the ruling party militia.

The MDC accuses the police and the government of trying to harass and frighten Mr. Coltart.

Ten priests and lay clergy who were arrested and held in police cells in Bulawayo in recent days have been given bail on charges of causing a public obstruction. They were arrested while holding a prayer vigil for peace in Zimbabwe.