MEXICO CITY, June 20 (Xinhua) -- Six people were killed and more than 100 others wounded on Sunday in a violent clash between police and teachers in the southern Mexican city of Oaxaca, authorities said.

The six deaths were civilians, while the injured included 55 federal and state officers, Oaxaca state public security official Jorge Alberto Ruiz Martinez was quoted as saying by media reports.

Mexico's National Security Commission said Sunday that the police "were not armed and didn't even have batons," in their efforts to end the protesters' week-long blockade of a road in Oaxaca.

It added that the gunshots came from unknown gunmen and demanded a local investigation.

A total of 21 people were arrested by 14:30 p.m. local time (2130 GMT), local daily Milenio quoted Hector Gonzalez Hernandez, health minister of the Oaxaca state, as saying.

The protest in the state capital was among a renewed wave of protests the National Coordination of Education Workers (CNTE) staged from May 15 against President Enrique Pena Nieto's education reform enacted in 2013.

The reform requires Mexican teachers to undergo performance evaluations in an effort to improve the country's poorly rated education system. It aims to remove the powers unions have over jobs and end the practice that teaching positions were inherited or sold.

The recent round of protests, held in Mexico City and states of Chiapas, Guerrero, Michoacan and Oaxaca, became more furious after the arrest on June 12 of Ruben Nunez, a CNTE leader in Oaxaca, for alleged money laundering.

During a news conference in Mexico City on Sunday, CNTE leaders denounced the government repression of Oaxaca protesters, asked for the release of Nunez and his deputy Francisco Villalobos, while reiterating a call for talks with the government to resolve the confrontation.

The CNTE has proposed to revise a few provisions in the reform program, which they believe violate their labor rights.

It also announced at the news conference continued protests on Wednesday, to be followed by another one in Mexico City.