STORY: Protesters attacked a security barricade erected outside the country's presidential residence in Zocalo square. Demonstrators demanded that justice finally be done for those killed.
In 1968 security forces stormed a leftist student rally in Mexico City's Tlatelolco district, killing 30-40 people, according to officials. But rights activists say as many as 300 were killed.
The student massacre took place just days before the opening ceremony of the country's 1968 Olympic Games.