Vigilante justice is not uncommon in Mexico, particularly in rural, indigenous areas where there is a lack of police officers and mistrust of state institutions runs deep. But the spread of drug and organized crime gangs into remote regions in recent years has worsened the sense of lawlessness there, creating the kind of flare-ups in violence that the new government of President Enrique Peña Nieto has promised to control with a planned paramilitary force.

The new vigilante movements join older, more established citizen police forces in Guerrero State, some dating to 1995. Before the outbreak this month, the vigilante movement already claimed to be the law in 77 towns and villages in the state. The movement has also spread to Colonia Lebarón, in the border state of Chihuahua, where residents set up a civilian defense force in 2009 after two residents were murdered, and Cherán, in Michoacán State, whose residents expelled the police in 2011, closed entrances to the town and armed themselves against violent illegal loggers believed to be protected by criminal syndicates.

In Ayutla de los Libres, the citizen police squads have built their own checkpoints, copying the other grass-roots police movements in the region. The fate of those arrested, who are suspected of extortion and kidnapping, is uncertain. Abel Barrera Hernández, a human rights official in Tlapa de Comonfort, Guerrero, said residents would investigate the offenses and hold a public trial by month’s end.

There are no independent estimates of how many people are participating in these efforts. But movement leaders expect more and more communities to join in.

“The most important weapon will be the organization of the people,” said Bruno Plácido Valerio, who helps organize community policing in Guerrero. He said he had been getting regular calls from other community leaders who want to join the movement.