Three more people were arrested as police broke up violent protests near the venue where John McCain was to be officially nominated as Republican presidential nominee last night.

Police used tear gas and grenades to prevent the protesters from getting closer to the Xcel Energy Centre, venue of the Republican National Convention, as President Bush addressed delegates via satellite from the White House.

The protesters, about 2,000, were holding an anti-poverty demonstration just a day after another group caused damage to buildings as they marched against the Iraq war. A self-described anarchist group called The RNC Welcoming Committee claims it disrupted the convention. It hints at more trouble in the days ahead. The group is not officially connected to organisers of either of the marches on Monday or on Tuesday.

Cheri Honkala, a leader of the Poor People's Economic Human Rights Campaign that called the protests, asked marchers to be nonviolent.

She told anarchists in the crowd that she would hold them responsible if they interfered in the peaceful march. It was the third day of protest marches in downtown St Paul since delegates began arriving last weekend.

More than 3,500 police officers have been deployed in the city to handle security, with street protests their key brief.

Many streets in the city have been closed to traffic making many people accessing the city to travel long distances.

On Monday, more than 200 people were arrested following daylong protests at the city. The anti-Iraq war protesters smashed windows of shops and damaged a police car, but their plans to set it ablaze were stopped by police.