Striking teachers, some armed with machetes and guns, hijacked and burned buses and blocked highways Thursday in their monthlong battle with the government of the Mexican state of Oaxaca.
The increasingly violent clashes threatened to last through Mexico's July 2 presidential election and potentially disrupt voting in the region.
Police officials said teachers blocked most federal and local roadways in an attempt to stop a march in support of Oaxaca state Gov. Ulises Ruiz, who last week ordered police to force protesters from Oaxaca City's main square where they had camped out to demand a salary hike.
Protesters have called for Ruiz's ouster and mounted the blockades to try to turn back buses carrying government supporters, many of whom were believed to have been summoned by the governor himself.
Mexican newspaper Reforma reported on its Web site that the pro-Ruiz march, which was organized by local business groups, took place after only an hour's delay.
Police said the protesters torched at least two buses, and some attended the blockades armed with sticks, machetes, and guns, police said.
On Monday, the teachers broke off negotiations with authorities and blockaded government offices after federal officials said they could not meet their pay demands.
Union leaders representing the teachers said federal officials told them they would have to negotiate their demands with state officials. But state officials say they can't afford a large, one-time pay hike.
In Mexico, the state and federal governments share responsibility for schools.
Teachers on Thursday were also asking Mexico's Roman Catholic Church to help mediate the conflict.
Some have expressed fears that the monthlong conflict could disrupt voting in Oaxaca on July 2, when Mexico will elect a new president and congress.
Ruiz has accused local representatives of presidential candidate Andres Manuel Lopez Obrador's leftist Democratic Revolution Party of aiding and provoking the protests.
Ruiz belongs to Mexico's Institutional Revolutionary Party, which has governed the state since the party was founded in 1929.
Mexican Deputy Interior Secretary Arturo Chavez told reporters in Mexico City on Thursday that federal officials had no confirmation of Ruiz's allegations.
Chavez said the federal government was urging teachers to restart negotiations with state officials and said he could not do anything about the teachers' demands for Ruiz's resignation.
"He was elected by all Oaxacans, he is the constitutional governor of the state," Chavez said. "As a result, we reiterate our call for prudence and an agreement that we can resolve these differences through dialogue.
Dozens of people were slightly injured in last week's raid aimed at moving the teachers from the arch-lined square, a major tourist attraction in this colonial city of 245,000 about 350 kilometers (220 miles) southeast of Mexico City.
Teachers later re-established their tent city in the square.