Thousands of Mexican teachers from a radical union marched in Mexico City to protest an education reform and the arrest of two of their leaders.

The demonstration along Mexico City's main boulevard capped days of protests in impoverished southern regions where teachers blocked roads.

The CNTE union opposes a reform by President Enrique Pena Nietom enacted in 2013, requiring teachers to undergo performance evaluations in an effort to improve the country's poorly rated education system.

The education department has vowed to fire teachers who refuse to take the tests.

The reform aims to remove the power that unions have had over jobs and end the practice in which teaching positions were inherited or sold.

Much of the resistance to the reform has come from the states of Oaxaca, Guerrero, Michoacan and Chiapas.

Protesters were also angry about last weekend's arrest of the leader of the CNTE's Section 22 based in Oaxaca state, Ruben Nunez, over allegations that he received illicit funds and laundered $1.3 million.

His deputy, Francisco Villalobos, was detained on charges of stealing text books.