Eight people were killed by a group of gunmen during a birthday party at a ranch in the northwestern Mexican state of Sinaloa, media reports said.

Around a dozen men travelling in two SUVs arrived at the ranch outside the town of Bachoco and began firing at the party-goers, the daily Reforma reported Saturday on its online edition, citing information from municipal police.

After forcing their victims to lie face down, the assailants starting firing. Seven people died at the scene of the massacre while another person perished at a hospital in Navolato.

Two other people also were wounded, according to Reforma.

Experts with the Sinaloa Attorney General's Office found 100 shell casings from AK-47 assault rifles, weapons commonly used by Mexico's well-armed drug cartels.

The Televisa network reported the killings without providing any details, but said the information had been confirmed by Sinaloa state police.

Sinaloa, bastion of a drug cartel and birthplace of Mexico's leading kingpins, is among the states hardest hit by drug-related violence that has claimed more than 17,000 lives nationwide since December 2006, when newly inaugurated President Felipe Calderon militarized the struggle against organised crime.