Heavily armed men killed at least 16 people, all members of a ranchers' association, in two different massacres in southern Mexico over the weekend, Mexican media said on Sunday.

Some 40 men riding in luxury vehicles and wearing uniforms of an elite police squad shot nine people dead in the town of Petatlan in the state of Guerrero on Sunday, El Universal newspaper reported.

And a group toting automatic weapons killed seven people in the town of Iguala, also in Guerrero, on Saturday.

Reforma newspaper said the ranchers were holding a meeting in Iguala and at least two of the sons of the association's state leader, Rogaciano Alba, were killed in Sunday's attack.

Alba himself has survived two other attacks in the past, Reforma said.

The newspapers did not say what could have triggered the attacks but well-armed drug traffickers are active in Guerrero, a poor, mountainous state on the Pacific coast home to the Acapulco beach resort.

Clashes over land rights or local politics are also common in Guerrero.