Thousands of Tamil Canadian protesters who blocked all lanes of a downtown Toronto highway for several hours Sunday evening began walking away from the area around midnight.

Tamil protesters waving red flags shut down a downtown Toronto highway on Sunday evening. (Patrick Dell/Canadian Press)A spokesman for the protesters told TV station CP24 that Liberal Leader Michael Ignatieff's deputy chief of staff has promised to bring up their concerns Monday in caucus about the civil war in their native Sri Lanka and the possibility of economic and diplomatic sanctions by Canada.

The demonstrators were happy with the response and said they'd leave the Gardiner Expressway and take their protest to the Ontario legislature at Queen's Park, he said.

The eastbound and westbound lanes of the elevated expressway were completely blocked by people, including mothers with children, who marched up the ramps at Spadina Avenue about 6:30 p.m. ET and on to the highway that runs across the south end of the city.

Traffic on the major thoroughfare was backed up in both directions for several kilometres.

Police estimated as many as 2,000 protesters took part in the demonstration, which was mainly peaceful with some reports of minor skirmishes with police. Hundreds sat down, linking arms and chanting "no more genocide."

Local media also reported Sunday that police had temporarily shut down southbound access to the Don Valley Parkway at Highway 401, in the city's north end. The parkway links with the Gardiner in the south.

For several months, Tamil Canadians and their supporters have been holding demonstrations in Toronto and Ottawa to protest violence in northern Sri Lanka. They are calling for foreign governments to help arrange a ceasefire between Sri Lankan government troops and the Liberation Tigers of Tamil Eelam insurgents.

Meeting demanded

Earlier Sunday evening, protest spokesman Siva Vimal vowed that protesters would stay on the highway until they obtained a meeting with federal officials.

Police Chief William Blair said several protests downtown had spread his resources thin on Sunday. (Nick Czernkovich/CBC)"We are not going to move until a representative from our federal government comes here … from Prime Minister [Stephen] Harper's office … and addresses this crowd and tells us specifically what they are going to do to take action on implementing a halt to the war in Sri Lanka."

Mayor David Miller told TV station CP24 that Tamil Canadians have the right to demonstrate but that shutting down the expressway doesn't help their cause and they don't have the right to do that.

"It's extremely dangerous for them to be on the Gardiner," he said, adding that he was concerned about the protesters' safety and that of the public and police.

Miller said it's the responsibility of Toronto police to handle such protests, adding he was confident they would handle it and "bring in whatever resources are necessary to ensure public safety is preserved."

Police chief calls for more officers

At a news conference late Sunday evening, police Chief William Blair said the protesters had spread his resources thin with several protests downtown. He had officers in place at the Gardiner as well as at the Ontario legislature and the U.S. Consulate, where protesters began another demonstration earlier Sunday.

Blair said he was calling in more officers across the city, including those from the Ontario Provincial Police and other police services, and would take action at some point if negotiations failed to reopen the expressway.

But he added that police would handle protesters "with minimal amount of force."

Police were worried that moving the demonstrators off the Gardiner could cause a stampede, he said.

"I'm very concerned about the safety of children," Blair said. "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."

In a separate demonstration, about 1,000 Tamil protesters blocked traffic in front of the Ontario legislature at College Street and University Avenue. The office of Premier Dalton McGuinty said there would be no official comment on the situation until Monday.

The latest protests came one day after reports that an all-night artillery barrage in Sri Lanka's war zone killed at least 378 people and forced thousands of civilians to flee to makeshift shelters along a beach.

Last week, International Co-operation Minister Bev Oda met with Sri Lankan Foreign Minister Rohitha Bogollangama to discuss the civil war.

Oda said Canada will provide an additional $3 million in humanitarian aid for Sri Lanka, while calling on the country's military and rebels to commit to a ceasefire that will allow civilians to escape the war zone.

With files from The Canadian Press