Three members of an elite state police force and a civilian were killed and another officer was seriously wounded in an attack by suspected drug cartel hit men on a police vehicle in this northern Mexican city.

The security spokesman in Coahuila state, Sergio Sisbeles, told Efe the incident occurred around 11:30 a.m. Thursday when the four state law-enforcement officers were on patrol.

He said the attack was an act of revenge by organized crime elements after two suspected cartel enforcers were arrested Wednesday in possession of high-caliber weapons and turned over to federal prosecutors.

One unidentified male passerby was also killed in the attack.

Members of the Coahuila state Attorney General's Office who arrived at the scene to investigate confirmed the deaths of the three police and the civilian.

Comarca Lagunera, a metropolitan area straddling parts of the northern states of Durango and Coahuila where the attack occurred, has seen an uptick in violence in recent years stemming from a turf war between the Sinaloa and Los Zetas cartels, Mexico's two most powerful drug mobs.

Organized criminals have carried out massacres, shootings at bars and even bomb attacks on media outlets in that metro area.

Security has been bolstered in the Comarca Lagunera in recent days with more army soldiers and federal police arriving to support the efforts of the Creditable State Police, a recently created elite state law-enforcement agency.

Conflict among rival cartels and between criminals and the security forces has claimed more than 50,000 lives in Mexico since December 2006, when newly inaugurated President Felipe Calderon - whose term ends in December - militarized the struggle against drug trafficking. EFE