Several NGOs had called on the army to stop patrols in Guerrero and Chiapas, where the Popular Revolutionary Army (EPR) and the Zapatista National Liberation Army (EZLN) operate.

BBC: Mexico urged to stop Chiapas patrols

The Zapatista uprising began in January 1994, when the rebel Zapatista National Liberation Army, led by a man known only as "Subcommandante Marcos" declared war on the central government in an effort to gain improved living conditions and better rights for indigenous Indian peasants in the southern Chiapas region.

BBC: Mexico urged to stop Chiapas patrols

On 1 January of that year, the North American Free Trade Agreement was signed and the National Zapatista Liberation Army -- made up of local indigenous people -- occupied four towns in Chiapas while calling for better conditions for indigenous people and the protection of communal lands.

BBC: Through Mexico��s Mayan heartland