Acapulco - Gunmen stormed a house and shot dead a family of five, including a grandmother, a three-year-old boy and a pregnant woman in the Mexican resort of Acapulco on Wednesday, prosecutors said.

The killings are the latest in a recent wave of murders in the city, where rival drug cartels fight for Pacific trafficking routes, street corner dealing and protection rackets.

Gunmen entered the house in the working-class neighbourhood of Cinco de Mayo, about six kilometres from the ocean, in the early hours of the morning, an official from the state attorney general's office said.

The attack bore signs of the cartels, but the motive was unclear, said the official, who asked not to be named for security reasons.

The victims also included a 30-year-old man and a young woman. Cartel gunmen often kill the families of their targets.

The attack brings the murder toll to 25 in less than a week in Acapulco, the resort that once drew stars such as Elvis Presley and Johnny Weissmuller.

Across Mexico there have been more than 55 000 drug gang-related deaths since President Felipe Calderon took power in December 2006 and declared an offensive on the cartels.

Incoming president Enrique Pena Nieto, who will take power in December, has promised to reduce the rates of homicide, extortion and kidnapping. - Reuters