Fifteen police officers were killed in a gang ambush in western Mexico, an official said, marking the deadliest day in recent years for security forces battling the drug war, reports the Agence France Presse.

Five more officers were wounded in Monday's assault, which took place on a twisting rural highway near the village of Soyatan as a convoy carrying the elite state police unit headed to Guadalajara, Mexico's second biggest city.

Authorities suspect the powerful "Jalisco New Generation Drug Cartel" carried out the assault against the officers after waiting for them in a makeshift encampment for one or two days.

The assailants blocked the road with vehicles, pouring fuel on them and setting the cars on fire, said Francisco Alejandro Solorio Arechiga, Jalisco's state security commissioner, who said a "large number" of them attacked the officers.

Authorities say the Jalisco attack appeared to be in revenge over the arrest of four gang suspects in an investigation into a failed assassination attempt against Solorio in March.