Teachers were marching in the Brazilian city of Curitiba on Wednesday to oppose a change to state pensions.

Video images on the website of local newspaper Gazeta do Povo showed police firing tear gas at protesters as they approached the Parana state legislative assembly. A vote was being held to change the terms for teachers' pensions.

Police said they took action after a few protesters tried to gain access to the assembly building. The live television pictures showed police firing rubber bullets into groups of teachers. Water cannon were also used to drive demonstrators back. The police action has been criticized as heavy handed.

Up to 150 protesters were injured. "We have opened the city council building for people injured (in the protests). It looks like a war zone," Gustavo Fruet, mayor of the city of Curitiba, said on Twitter. Security forces said about 20 police officers were hurt.

Fruet described the scene as a "war without precedent" in the city. The city's unarmed security officers had formed what Fruet called a security corridor to allow injured teachers to reach the city hall building and received first aid. He blamed what he called a "tragedy" on the security forces, who are under the control of the state government.

The Parana state government said in a statement on its website that it "deeply regrets the acts of confrontation, aggression and vandalism caused this afternoon by protesters" not associated with the striking teachers. Seven people were arrested for attacking policemen.

Despite the protests, the changes to the state pension system were approved in the legislative assembly. It means 33,000 retirees are to be moved from a pension paid for by the state, to one shared by the state and working teachers.

jm/bw (AFP, Reuters)