Police arrested three men who confessed to hurling grenades into a crowd on Independence Day that killed eight — and said they belonged to the deadly 'Zetas' gang of guns-for-hire, officials said Friday.

The attack on a crowd of civilians Morelia city on September 15 shocked the Mexican government into posting a 10-million pesos (UD$1-million) reward for information leading to the arrest of the perpetrators.

The men, arrested after an anonymous telephone tip, told federal police "that they were the ones who detonated fragmentation grenades" in downtown Morelia during the main Independence Day celebration, said Marisela Morales, an official with the office of Mexico's attorney general.

At least 106 people were injured in the Morelia attack, police said.

The men "also said they formed part of the criminal organization of the Zetas" and have been engaged in criminal activities in the state of Michoacan, Morales said.

The Zetas are paramilitary gang of hitmen that work for the powerful Gulf of Mexico drug cartel.

The original Zetas were elite Mexican Special Forces soldiers trained to find and detain drug lords. A group of deserters formed the group when they instead went to work for the drug lords in the late 1990s.

The Morelia attack took place amid a wave of organized crime violence that has killed more than 3000 people across Mexico since the start of the year.

AFP