Policemen fire rubber bullets and tear gas against teachers during a protest in Curitiba Thomson Reuters RIO DE JANEIRO (Reuters) - More than 100 people were injured on Wednesday in violent clashes between protesters and police in the Brazilian city of Curitiba, where teachers were marching to oppose a change to state pensions, the city's mayor said.

Video clips on the website of local newspaper Gazeta do Povo showed police firing cans of tear gas at protesters as they approached the legislative assembly for the state of Parana, where a vote was being held to change pension terms for teachers.

Some protesters could be seen wearing motorcycle helmets and using trash bin lids as shields.

"We have opened the city council building for people injured (in the protests). It looks like a war zone," Curitiba Mayor Gustavo Fruet said on twitter, adding that more than a hundred had been injured.

Despite the protests, the changes to the state pension system were passed with 33,000 retirees being moved from a pension paid for by just the state to one where the cost is shared between the state and working teachers.

The state government of Parana said it "profoundly lamented" the violence on its Facebook page, adding that seven people had been arrested.

The clashes come at a time when states across Brazil are being forced to reign in spending as the country imposes an austerity drive to try and escape recession. \

(Reporting by Stephen Eisenhammer; Editing by Bernard Orr)