Masked protesters with machetes forced passengers off a city bus and set it ablaze Thursday in this southern Mexican city held hostage by demonstrations and violence.
The violence came as teachers were expected to vote on ending a strike that has kept 1.3 million children from going to school for five months. But by Thursday afternoon, they had been unable to reach an agreement.
Bystanders were able to put out the flames on the burning bus and no one was injured.
Oaxaca has been on edge since late May, when teachers walked off the job to demand better salaries and benefits. The strike turned into a broad movement after police attacked the strikers in the city's colonial center the next month.
Sympathizers from varied left-leaning groups joined the teachers, and have built barricades, taken over radio stations and newspaper offices, driven out police and other state authorities and scared away tourists from this city popular for its handicrafts, cuisine and colonial architecture.
Chief among their demands is the removal of state Gov. Ulises Ruiz, whom they accuse of rigging his own election and sending armed thugs against protesters. He denies the charges and has refused to step down.
At least five people have been killed in violence related to the protests.
Because there are no police patrols, masked and armed protesters roam the streets, seizing anyone they suspect of criminal activity. Often, they grab young men accused of trying to commit various crimes, tie them up for hours and beat them.
Also Thursday, protesters retreated from one of the radio stations they seized in August. Protest leader Florentino Lopez said the government had disrupted the transmission and they were no longer able to broadcast their messages.
The state government has repeatedly asked federal authorities to send in troops, but President Vicente Fox has instead tried to broker peace negotiations that have made little progress.
Some teachers have defied the union and opened schools, but protesters often block children and their parents from returning to classes.
Protesters have pledged to blockade highways, beef up barricades and boycott commercial centers Friday. If Ruiz doesn't step down, they say they will try to keep President-elect Felipe Calderon from taking office on Dec. 1.