At least 40 people were injured when police clashed with protesters in Mexico City during a demonstration commemorating the 45th anniversary of a student massacre.

CEOAFRICA.com gathered that some of the protesters threw firebombs, bottles and rocks at police who battered to disperse the crowd.

The rally marked the anniversary of the 1968 killings of student protesters in Tlatelolco Square.

Official reports at the time said 25 people died, although rights activists say as many as 350 may have been killed.

The anniversary of the killings is often marked by protests and violence.

In the latest clashes, police said 20 officers had been injured and 20 people were arrested. Authorities said anarchists had infiltrated the march.