Authorities are investigating allegations that an armed group abducted at least 11 people after occupying a town in Mexico's troubled southern state of Guerrero last week, prosecutors said Tuesday.

The group had arrived in Chilapa on May 9, describing itself as vigilante "community police" seeking justice against a local drug gang before leaving on May 14.

Guerrero state chief prosecutor Miguel Angel Godinez Munoz said authorities are investigating whether it was really one of the state's legal community police forces or a group infiltrated by a gang.

Chilapa, a majority ethnic Nahua town, is at the center of a turf war between two gangs, Los Rojos and Los Ardillos.

The armed men left Chilapa after an agreement with the government, which included the resignation of the local police chief.

In return, the group agreed to return weapons it had taken from the municipal police.

The townspeople held protests against the presence of the 300-strong group.

Residents have reported the disappearance of four people as well as the abduction of 11 others, Godinez Munoz said.

"They say they were accompanying their relatives when they were snatched by the group of armed citizens," he told Radio Formula.

The prosecutor said he does not have credible information to confirm claims that as many as 30 people have gone missing.

Ramon Navarrete, president of the Guerrero state human rights commission, said he received reports of 13 people who were kidnapped.

Jose Diaz Navarro, representative of the families of the missing, told the Milenio news website that the armed men "took away young men they accused of being 'halcones' (hawks)," a term used for people who work as lookouts for gangs.

Matilde Abarca, mother of a missing man, said the group accused her of charging people a protection tax when they took him away.

"But in reality, my son is a shopkeeper," she told Milenio.

Earlier this month, a candidate for mayor from the ruling Institutional Revolutionary Party (PRI) was killed ahead of the June 7 elections.

In November, 11 decapitated bodies were found near the town.

Chilapa is in the same region as Iguala, a city where prosecutors say local police abducted 43 college students in September and delivered them to the Guerreros Unidos drug gang, which slaughtered them.