Twenty-five people were killed in southwest Mexico, including nine minors, in a bus crash on Sunday.

The accident happened within the municipality of Buenavisa de Cuellar, in the northern part of the state of Guerrero, about 150 kilometres south of Mexico City.

A further 23 people were injured in the crash.

Buenavisa de Cuellar is 150 kilometres south of Mexico City.Buenavisa de Cuellar is 150 kilometres south of Mexico City.

The passengers were headed to a political rally in Buenavista de Cuellar for Mexico's Democratic Revolution Party. Mexico is in the midst of campaigning for presidential elections on July 1.

The bus's brakes gave out and it flipped over into a 300-metre-high ravine, Guerrero's undersecretary of state for civil defence, Constantino González Vargas, told Mexico's El Universal newspaper.

A spokesperson for the Democratic Revolution Party pleaded for the state government to work as quickly as possible to recover the bodies of the victims so that they could be returned to their families.

With files from The Associated Press