For the second day in a row, protesters and riot police traded more than just words at a summit on expanding free trade throughout the Western Hemisphere.

Water cannon and tear gas were used to push back hundreds of demonstrators intent on once again tearing down part of the three-metre-high fence. A section of the barricade was breached Friday night.

Some people in the crowd hurled Molotov cocktails and chunks of concrete at officers who stood guard at the perimeter. A few protesters ran towards the fence and tried in vain to topple it with ropes.

Late Saturday, the RCMP said that a total of about 150 demonstrators had been arrested since Friday afternoon.

Dozens of people, including police officers, were also treated in hospitals, according to the Quebec City Regional Health Board. Some had cuts; most suffered from exposure to tear gas. There were also unconfirmed reports of wounds from rubber bullets.

Like the fence surrounding the summit site, there was clear division over whether police responded with the right level of force. Protesters who came expecting peaceful demonstrations said they were appalled by the actions of both sides.

Others hurled accusations squarely at riot police, accusing the officers of taunting the crowd by pounding their shields with clubs. They also said using tear gas and water guns was unnecessary.

During a news conference Saturday night, Prime Minister Jean Chrtien once again praised police for what he called proper restraint in maintaining crowd control. He blamed the clashes on extreme protesters determined to disrupt the summit.

Elsewhere in the provincial capital, roughly 30,000 people staged a peaceful march through the streets, chanting their opposition to globalization.

Labour groups from across North, Central and South America took part in the walk. Most of the union delegates joined human rights activists and environmentalists in peaceful rallies away from the security fence.

But some of them broke away from the main march and decided to join a group of protesters resolute on knocking down the security barricade.

The running battles began at about 12:30 p.m. eastern time, when a small group of demonstrators showed up at the fence and began climbing it. Police with water cannon responded by turning two hoses on them.

A few minutes later, lines of police swept in from a side street and pushed the crowds back. There were several arrests shown live on CBC Newsworld.

People were eventually moved away from the fence. But within a couple of hours, protesters had returned in even larger numbers. The ranks of officers in riot gear had also swollen.

The crackle of exploding tear canisters could be heard as some people tried to topple the barricade again.

By the middle of the afternoon, two lines of demonstrators at another location managed to attach ropes to a section of the security fence and tug as hard as they could. But they failed to pull it to the ground.

RCMP Const. Julie Brongel told Don Newman on CBC Newsworld that police didn't get Friday night's crowd under control until 3 a.m. ET Saturday. The Mounties were bracing for similar confrontations early Sunday.

Quebec City was not the only scene of protests Saturday. In British Columbia, police shut down the Peace Arch border crossing between Canada and the U.S. when about 2,000 demonstrators staged a peaceful rally.

Marches were also held in several cities across Canada.

Far from the demonstrations, delegates to the summit strolled through a quiet neighbourhood in the old part of Quebec City. They posed for a group photo, before Chrtien headed off to a news conference.

He said all of the leaders had agreed to limit membership in the proposed free trade zone to democratic countries.