Thousands of union workers, public school teachers and other critics of the Ontario government protested in downtown Toronto on Saturday, as the governing Liberals and hundreds of delegates convened to select a new party leader.

At its peak, the mass of protesters was estimated to be 10,000 to 15,000, the CBC’s Steven D'Souza reported.

However, just after 4:15 p.m. ET, the area in front of the Mattamy Athletic Centre, the former Maple Leaf Gardens, was all clear as the protestors departed.

The groups taking part in the protest included members of the Ontario Federation of Labour, the Ontario Public Service Employees Union, the Canadian Auto Workers, as well as major public-sector teachers' unions.

While many of these larger groups were in Toronto to protest the government’s anti-strike legislation used to impose contracts on teachers, D’Souza said there were other smaller groups present Saturday for separate issues involving the government.

Some protesters gathered outside the leadership convention from the early morning, while a much larger mass of protesters participated in a march that began in nearby Allan Gardens and circled past the convention.

Toronto police commended protest organizers for keeping things peaceful and without incident on Saturday, D'Souza said.

New premier to be named

The Liberals are in the midst of a leadership renewal process that was prompted by the resignation of Premier Dalton McGuinty, who announced that he was stepping down in October but agreed to stay on until the party selects a new leader.

The Liberals enraged many educators in the public school system by imposing contracts on elementary teachers through the use of controversial legislation that also gave the government the power to quash strikes.

While the government has since repealed Bill 115, also known as the Putting Students First Act, the rift between the teachers and the Liberals has not been healed. That's the same legislation that many unions have opposed, including those involved in the protest on Saturday.

Public elementary teachers launched a series of rotating, one-day strikes in December to protest the bill.

The Elementary Teachers' Federation of Ontario said some of its members would be in Toronto Saturday "to protest the damage that continues to be done to public education by the Ontario Liberal Party and Bill 115."

For the majority of the nine-plus years that the Liberals have been in power in Ontario, they had enjoyed the support of public-sector teachers.

With files from the CBC's Steven D’Souza and The Canadian Press