Protesters clashed with riot police in Mexico City on Wednesday, leaving dozens injured as thousands of people marched to mark the anniversary of a massacre of students in 1968.
The Red Cross said at least 51 people were injured as a group of masked protesters threw rocks and firebombs at police who used tear gas and threw stones back at them.
The city's public security department said 32 officers were injured by mostly masked and "self-declared anarchists." At least 97 people were detained.
Dozens of protesters broke the windows of stores, bus stops and a national newspaper office. Police officers used shields to defend themselves but also charged at protesters and journalists alike.
At least 10 journalists were hit by both police officers and protesters, according to the press rights group Articulo 19. Two other reporters were detained.
Three AFP journalists were among those attacked by police and were lightly injured. An AFP video journalist was attacked by protesters who used an aerosol can to blow fire at him, and broke his camera.
Hector Serrano, the city's government secretary, told Formula radio most of the protesters marched peacefully "but there were some 200 and 250 anarchists who are attacking officers."
The demonstrators marched to demand justice for the killings that took place on October 2, 1968, when soldiers opened fire on 8,000 protesters in the capital, leaving an official death toll of 40 while civil organizations say as many as 300 were killed.
This year, the demonstrators were joined by striking teachers who have held several protests in Mexico City since August against education reform championed by President Enrique Pena Nieto.
Demonstrations are held every year to mark the massacre in the Tlatelolco neighborhood, and it was the first march since the old ruling Institutional Revolutionary Party (PRI) returned to power after a 12-year absence.
The violent repression of 1968 occurred in the middle of the PRI's long reign in Mexico.
The party held power for 71 years through a mix of rigged elections, corruption and patronage until it was voted out in 2000. Pena Nieto, who took office in December, has pledged that the PRI has embraced democracy.
"It was after the student movement of 1968 and the successive political reforms that today we enjoy a pluralistic and democratic Mexico," Pena Nieto wrote on Twitter.
But protesters criticized the PRI and Pena Nieto, demanding that those responsible for the massacre finally face justice.
The president at the time, Gustavo Diaz Ordaz, later took responsibility for the repression but he died in 1979 without facing justice.
"There must be justice and reparations," said Emilio Reza, a member of the 68 Committee comprised of survivors and their relatives.