At least 10 people were killed and nine wounded on Saturday when gunmen attacked a group of amateur rally drivers in the northern Mexican town of Ensenada, near the US border, authorities said.

The motorists, who were participating in a race, were parked on the side of a highway when a group of men got out of a pickup truck and opened fire.

The attack "left nine wounded and 10 people dead," Ensenada authorities said in a statement.

The prosecutor's office of the state of Baja California, where Ensenada is located and which has been hard hit by drug violence, announced the formation of a "special investigation group" to identify the killers and determine the motives behind the shooting, the statement said.

Some of the wounded received emergency care and were later transferred to hospitals in Ensenada, a municipality of some 440,000 people.

Baja California is among the Mexican states with the most intentional homicides, the majority attributed by the government to violence between organized crime groups.

Between January and April, 721 murders were committed there, according to official data.

Baja California and five other states accounted for nearly half of the 9,912 homicides recorded in the country in the same period.

Violence in Mexico has left almost 400,000 dead and tens of thousands disappeared since 2006, when the government deployed a controversial anti-drug offensive with the support of the United States and the participation of Mexican armed forces.