Mexican authorities are investigating the disappearance of three Italian men in the western state of Jalisco.

Vicenzo Cimmino, Raffaele Russo and Antonio Russo - all from Naples - were last seen on New Year's Eve in the Tecalitlán municipality.

Some reports say the Italians went missing after being detained by police at a petrol station.

Italian diplomats are helping the investigation, the Mexican authorities say.

Last weekend, family members and friends of the missing men marched on the streets of Naples, demanding answers from the Mexican government about what had happened to their loved ones.

Last year was Mexico's most violent year on record, with more than 25,000 murders.

Organised crime - and feuding drug cartels in particular - accounts for nearly three-quarters of those deaths, officials say.

Jalisco is one of Mexico's most violent states, where corrupt police officials often collude with gangs.