They gathered at the scene of the killings, the village of Acteal, in the southern state of Chiapas, to remember the dead.

Thousands joined the commemorative march

The 45 victims - 21 women, 15 children, and nine men - were shot at point-blank range or hacked to death with machetes.

They were seen as sympathisers of the Zapatista rebels, who launched a brief uprising four years ago.

Mexican authorities say investigations are continuing, but they have ruled out theories that the army and police were involved.

Opposition groups and human rights activists continue to blame paramilitaries linked to the governing party for the massacre, which took place over eight hours.

Political rights

About 4,000 Indians, many of them wearing the black ski masks of the rebel movement, marched from Polho to Acteal, chanting anti-government slogans.

Outside the army base at Acteal they shouted: "Chiapas is not a barracks, army get out".

Roman Catholic Bishop Samuel Ruiz said that Acteal had become a monument to peace and hope of resurrection".

The 1997 killings dramatically increased tension in the impoverished southern state, where the Zapatista National Liberation Army rebelled in January 1994 demanding political rights for Mexico's Indians.

A truce was signed 12 days later, although paramilitary groups linked to the ruling Institutional Revolutionary Party (PRI) have been blamed for dozens of killings in Chiapas.

One conviction

The Mexican Government report into the killings attributed the massacre to simmering political and religious disputes between villagers.

More than 100 people have been arrested in connection with the massacre, and Attorney General Jorge Madrazo says the investigation is continuing. Only one person has been convicted.

The report concluded that there was no evidence of any link between those arrested for the massacre and the army or any political party.

But Mexican and international human rights groups have called for a deeper investigation, saying they believe Chiapas state officials and the army helped arm the paramilitaries.