Thousands of Mexicans have marched through downtown Mexico City to mark the 35th anniversary of a massacre of student protesters.
News reports say an estimated 15,000 people joined the rally at Tlatelolco Plaza Thursday.
The reports say small groups of demonstrators separated from the main march and smashed dozens of store windows, cars and spray painted slogans on walls. Police said they arrested about 75 people.
The march was organized to remember the violent events of October 2, 1968, when police fired on a crowd of largely peaceful student demonstrators in the plaza, demanding more democracy.
The government of then-President Gustavo Diaz Ordaz said 30 people were killed, but human rights groups say as many as 300 may have died.
The incident happened during Mexico's so-called "dirty war" against leftist insurgents. At the time Mexico was ruled by Institutional Revolutionary Party.
The party's 71-year hold on power ended when President Vincent Fox was elected in 2000.
Last year, Mr. Fox announced the opening of millions of top-secret files that could contain information on hundreds of political dissidents who disappeared during the crackdown.