Teacher union leaders in Mexico have called on the government to repeal an education reform they say penalizes teaching staff in rural areas, and say they could step up protests that have caused havoc in the south and culminated in angry clashes with police.
Tensions have risen in recent weeks as teachers opposed to President Enrique Pena Nieto's reform, which requires teachers to take evaluation tests every three years, have closed off a slew of highways throughout the country.
The attorney general's office is now investigating a clash last month in which nine people were killed in stand-offs with police in the southern state of Oaxaca.
The National Security Commission has denied that police used firearms against the protesters. A spokesperson for the Federal Police could not be immediately reached for comment.
Speaking to reporters Wednesday evening, members of Mexico's CNTE teachers union said that union factions could call on thousands more teachers to strike, close highways and shut Mexico's northern and southern borders if they choose not to accept the government's terms.
"This is a war," said German Mendoza, a teacher in Oaxaca. "We are going to keep mobilizing our communities, our families, and social organizations ... toward the repeal of the education reform."
Teachers say the evaluations, which compare educator performance nationwide, are poorly designed and ignore the teaching methods, curriculums and resources in rural areas.
Teachers who do not perform well enough on exams can be dismissed, which has led some of those opposed to the reform to say the government should invest more in educational training.
Rogelio Vargas, a leader of Oaxaca's Section 22, a combative faction of the teachers' union, said he had received death threats following protests and feared for his life.
Mexico's Interior Ministry, which oversees security, has conceded to one of several proposals to form a panel of education experts and teachers to evaluate the government's education plan, but has not agreed to repeal the reform.
Mexico's air force flew tons of grain to Oaxaca on Friday as teacher protests spread and road blocks led to dwindling food supplies in some remote regions.