Tens of thousands of people took part in a silent march in Mexico City on Sunday. The protest was called to be held one week after deadly clashes in the Oaxaca state that killed at least 10 people. Photo courtesy of Andrés Manuel Lopez Obrador

MEXICO CITY, June 27 (UPI) -- Tens of thousands of people in Mexico City protested on Sunday over recent violent clashes between police and a teachers union in the Oaxaca state that killed at least 10 people.

The protest on Sunday was called by Andrés Manuel Lopez Obrador, a former mayor of Mexico City, one week after the clashes between the National Coordinator of Education Workers union and Mexican state police.


Authorities said more than 4,000 police officers were deployed to central Mexico City as the march occurred Sunday.

The teachers union, social organizations and local residents held protests and disrupted traffic on a major highway connecting Oaxaca to Mexico City for about a week before violence erupted last Sunday when riot police attempted to disperse the crowds. Authorities said 10 people died, but some witnesses said up to 12 people died. Dozens of civilians and police were also injured.

The incident increased criticism against Mexican President Enrique Peña Nieto. Some say forces under the president's command use too harsh of a force against the opposition and protesters. Many in Sunday's protest called for the president's resignation.

"Condolences to relatives of the victims of repression in Oaxaca," Lopez Obrador, leader of the progressive Morena Party, said in a statement. "Enrique Peña Nieto: stop homicidal violence, seize the responsible and open dialogue."

The union has continued battling constitutional reforms passed by Mexico's Ministry of Education that would force teachers to take examinations to be approved for employment, with further tests to maintain jobs.