A DRUG gang has killed 20 people, including a mayor and his father, in the mountains of the southern Mexican state of Guerrero, officials said on Thursday.

Residents began burying the victims even as a video posted on social media showed men, who identified themselves as the Tequileros gang, claiming responsibility for the mass shooting.

The Guerrero state security council said gunmen burst into the town hall in the village of San Miguel Totolapan Wednesday and opened fire on a meeting the mayor was holding with other officials.