At least six dead after police 'open fire' on teachers in public protest

A federal police helicopter flies overhead as protesting teachers who were blocking a federal highway maintain their positions in the state of Oaxaca, near the town of Nochixtlan, Mexico

Sayra Cruz and Jose Maria Alvarez, in Oaxaca

Violent clashes between police and members of a radical teachers' union who had blockaded a highway in southern Mexico have left six people dead and more than 100 injured, officials said.

The activists from the National Co-ordinator of Education Workers, or CNTE, are opposed to the mandatory testing of teachers as part of education reform and are also protesting over the arrest of union leaders on money laundering and other charges.