TORONTO - Anyone wondering where the angry summit protesters were had their answer Friday as thousands marched in Toronto's streets and police in riot gear descended en masse to contain them.

After days of colourful and whimsical protests it was the city's first real taste of what police, and the city, have been bracing for.

What started as a peaceful gathering in a city park morphed into a massive march and tense standoff. Police held back demonstrators just north of the G20 summit security zone before the crowd turned back.

The imposing steel gates surrounding the security zone were forced to close early as the protest simmered. Police would only say "specific security concerns" prompted the action.

Gaetan Heroux, a protest organizer, called the "angry militant march" a great success that prompted a huge show of authoritarian force.

"It was a wonderful protest, the fact that we had close to 3,000 people," Heroux said.

"We said we weren't looking for confrontation."

The Integrated Security Unit said five G20-related arrests were made Friday, but did not specify if they were linked to the protest.

Protesters planned to spend the night in Allen Gardens, where the march began, and hoped to join other marches Saturday, he added.

What's been billed as the largest planned protest of the summit is scheduled for early Saturday afternoon outside the provincial legislature. Plans also call for a march through the city.

At one point during Friday's march a protester broke the police line and was dragged into the foyer of a building, setting off an angry response from the crowd.

"Let him go! Let him go!" they chanted. "We want justice!"

Others yelled, "Shame! Shame!"

Officers then aggressively waded in to push back protesters, who found themselves trapped on the sidewalk with nowhere to go.

One officer was even caught on video throwing a punch at a demonstrator, apparently hitting him in the face, prompting angry exchanges.

Protesters made finger guns outside police headquarters and made firing motions.

Three teens who got caught up in the confrontation described the sea of police blue as "unnecessary."

"We have a right to protest," said Kelly, 18, of Kitchener-Waterloo, Ont.

"And I didn't feel very comfortable being strangled by a cop just because I was standing on the street."

Her friend Mary, also 18, said she feared things would escalate once the police donned riot gear.

"Personally, I'm terrified," she said.

The massive crowd -- including a few women who marched bare chested in the bright sunshine -- headed south down University Avenue toward the summit security zone. Several hospitals and the U.S. consulate are on the broad roadway.

Several buses and vans packed with police officers raced to the scene to stop the march from getting closer to the security fence.

At the corner of University and Elm Street, riot unit police pounded on their shields, as mounted officers watched and one officer walked around conspicuously ready to fire tear gas, which proved unnecessary.

Several demonstrators taunted police, who for the most part kept their cool.

Police used their bicycles or riot shields to block off key intersections and keep protesters away from sidewalks and stores.

At one intersection where police in riot gear lined the road, a lone protester dropped his pants and mooned the officers.

The officers did not react and the protester left.

They eventually forced the march back to where it started, where tired demonstrators pitched tents, drummed and crashed on the grass. Officers surrounded the park, but kept their distance and did not interfere.

Organizers had vowed to set up a tent city near the summit security zone.

John Clarke, a protest organizer with the Ontario Coalition Against Poverty, called the police presence at the protest "offensive."

Earlier Friday protesters unveiled their version of the Harper government's $57,000 fake lake -- a children's splash pool with a deck chair.

It came complete with a sign: "Community organizers provide media lake for $12.99."

The tiny pool was set up outside a cavernous building in Toronto where media from around the world are gathered to cover the summit.

"Welcome to our pool party," said Adonis El-Jamal, spokesman for the Toronto Community Mobilization Network.

"Our pool only cost $12.99. Feel free to take a dip if you like," he invited reporters gathered outside the Princes' Gates at the Canadian National Exhibition.

Inside the media centre is the attraction that has turned into a form of political water torture for Prime Minister Stephen Harper.

The $57,000 fake lake features Muskoka chairs on a dock looking out on a small pool of shallow water.

A giant video screen displays scenes of Ontario's cottage country.

Protesters who gathered around the kiddie pool say the more than $1 billion spent on the summits could have housed all the homeless people in Toronto, along with all those on the waiting list for social housing, for one year.