Mexican police have fought running battles to dislodge thousands of striking teachers from the main square in the southern city of Oaxaca.
Teachers have now called a temporary halt to their protest
Officers fired tear gas as they evicted the teachers, who have been protesting over pay for the past three weeks.
Several people were hurt but officials denied claims that people had died.
The government says the teachers have agreed to attend talks on Thursday to try to end the strike, which has left a million pupils without classes.
The colonial city of Oaxaca, capital of the state of the same name, witnessed a series of clashes throughout Wednesday as police moved to evict the teachers from the central square where they had erected a tent city.
Helicopters flew overhead as officers dislodged the strikers only for them to retake the square several hours later.
By the end of the day, the square was cleared.
"The city is a battlefield," Sara Mendez of the Oaxacan Human Rights Network told the Associated Press new agency.
"Cars were burned. It's chaos."
Witnesses said shots had been fired but the state governor, Ulises Ruiz, denied a report by the teachers' union that three or four people had been killed.
The clashes left Oaxaca's streets strewn with debris
"They should tell us where they are because no policeman knows anything about this and no hospital has it registered, I think it is a lie," Mr Ruiz told a local radio station.
More than a million children have been unable to go to school since the teachers began their strike in May.
The state government in Oaxaca says it does not have enough funds to increase the teachers' salaries and has asked the federal government to step in.
Correspondents say the violence in Oaxaca and other clashes between police and protesting workers in various parts of Mexico have fanned tensions in the run-up to the 2 July presidential election.
The election is a close race between leftist Andres Manuel Lopez Obrador and conservative Felipe Calderon.