In another part of the tense city, thousands of campaigners marched through the streets in a peaceful protest. A group of 60 riot police drove the protesters back with water cannon and tear gas as helicopters hovered overhead. Running battles At least two protesters were arrested and security forces brought in earth moving equipment to help fortify the perimeter. Many demonstrators wore protective gear, ranging from handkerchiefs worn as masks to balaclavas to military-style gas masks. The BBC's Rob Watson says the use of water cannon would seem to indicate that police are adopting a far harder stance against the demonstrators.
Authorities blame the violence on what they call a small group of anarchist infiltrators.
A hemisphere of liberty' Just before noon on Saturday, crowds began to build again and taunt police. Leaders of countries from North and South America, Central America and the Caribbean spent the first day of the talks at a conference centre behind the security cordon. Summit working sessions were opened by Canadian Prime Minister Jean Chretien and US President George W Bush. This is not the time to grow timid or weary. He also pledged to listen the concerns of the campaigners outside the summit centre.