Thousands of Tamil protesters have left Toronto's Gardiner Expressway, after surging onto the highway to call attention to the escalating civilian death toll in Sri Lanka.

Around midnight, protesters began making their way down an on-ramp as police monitored the situation. Some told they planned to take their demonstration to Queen's Park.

Reporters and witnesses at the scene said the demonstration was largely peaceful. However, police arrested at least one person and video taken from a nearby highrise showed a bicycle being thrown at officers.

Activists demanded to speak to a representative of Prime Minister Stephen Harper about the civil war in Sri Lanka, but police said that would not be possible. Reports say the protesters agreed to leave the area because the Liberal party said it would address their concerns in Parliament.

Police Chief Bill Blair told reporters late Sunday it was an "unlawful and unsafe" protest, and the RCMP and the OPP were assisting. He said protesters gave no indication they were planning to take to the Gardiner.

Blair also said he was extremely concerned about the presence of children at the protest and said the elevated highway itself was very dangerous for people on foot.

"I'm very concerned about the safety of children, I think it's an extremely dangerous situation to put children on the front line of a protest in that way, I think it puts them at tremendous risk," he said.

Ghormy Theva, a protester on the Gardiner, told CTV Newsnet Sunday evening that demonstrations would continue until "definite" action was taken by the Canadian government.

At one point, more than 100 Toronto police were on the scene and had set up a perimeter on the highway. Vehicular traffic was severely backlogged on the Gardiner, a major thoroughfare in the city.

Officers on the scene were reportedly armed with tear gas, and police described the protesters as "uncooperative."

The national spokesperson for the Canadian Tamil Congress. David Poopalapillai, told CTV Newsnet Sunday that "desperate times call for desperate action."

But he said he was taken "off-guard" by Sunday's protest and said recognized the inconvenience it caused to motorists.

A second protest shut down the University Ave. and College St. intersection.

The protesters rallied after international news agencies reported nearly 400 civilians were killed during an overnight artillery bombardment. The Sri Lankan military is denying launching the assault that killed 378 civilians and wounded about 1,100.

Thousands are fleeing Sri Lanka's war zone as tensions between the military and Tamil Tiger rebels escalate.

Reports are hard to confirm because of a ban on journalists and aid workers in the war zone. Late Sunday, protesters disputed the death toll from the artillery bombardment, saying it was in the thousands.

The demonstrators protested in Toronto yesterday afternoon as well, marching through the city and ending up on the lawns of Queen's Park.

On Sunday, about 2,000 Toronto Tamils crowded several streets, making their way in front of the U.S. Consulate on University Avenue.