There have been clashes between demonstrators and police outside military barracks in the Mexican city of Iguala where 43 students disappeared in September last year.
The protesters accuse the military of involvement in the fate of the trainee teachers who are presumed dead.
The wife of a Mexican politician suspected of helping to plot their apparent massacre is to be put on trial.
The atrocity has sent shockwaves through Mexico and President Enrique Pena Nieto faces his deepest crisis over the government’s handling of the investigation.
