Montreal firefighters and their supporters trashed city hall Monday evening to show their outrage with legislation that would alter their contracts.

Hundreds of city workers stormed the building, throwing water, setting off smoke bombs, and chasing councillors from rooms.

Security guards whisked Mayor Denis Coderre from room to room in an attempt to avoid the mob when the crowd of placard-wielding demonstrators stormed council chambers just after 6:45 p.m.

Councillors were forced to run away until the demonstrators left, leaving behind papers strewn all over the floor.

City Councillor Karine Boivin-Roy was one of those who had to flee.

"They were able to come in and they slashed the door open to come in and they came here in the sacred institution. We tried to come back and they were even up on the balcony. They started throwing glasses, I got a glass on my hand and we were rushed out because it was getting dangerous," she said, adding that her paper notes from last November were lost.

Snowdon councillor Marvin Rotrand called it an attack on democracy.

"This is an effort to vandalize city hall... first of all it's to prevent democracy from going forward. City council, where there was some sympathy for their message probably dissipated," said Rotrand.

Other councillors said the protest was unacceptable.

"I understand opposite points of view, this is absolutely beyond appeal. Scandalous is the right word," said councillor Guillaume Lavoie.

Police stood idle, and Minister demands answers

During the protest Montreal police officers stood by, not even looking as protesters plastered stickers all over the walls of city hall and set fires outside.

On Tuesday morning Municipal Affairs Minister Pierre Moreau said that lack of action by police was "inexplicable."

He demanded Montreal's police chief, Marc Parent, step up and explain why police officers stood by as firefighters ran wild.

Parent is expected to address the protest at 11 a.m. Tuesday.

Council later returned to session amid the mess, as Mayor Denis Coderre urged calm.

"I ask all union executives to get control of their members" said Coderre as the session resumed once the protesters had left the building.

Hours before the protest Marc Ranger, spokesperson for the umbrella group representing all unions involved in the Bill 3 dispute, said that union members had to be careful not to lose public support, saying unions "need to be careful the way we choose to make this battle, not to lose public support.

After seeing video of the mess left after firefighters trashed city hall, Ranger said the protest was too much.

He also retracted a comment he made last week, saying the unions were ready to go to war.

"When I said last week that we would put more pressure on the government that is not what I meant," said Ranger.