Three people were wounded when unidentified assailants threw grenades at two auto dealerships in Ciudad Victoria, the capital of the northeastern Mexican state of Tamaulipas, state officials said.

The attacks occurred Wednesday afternoon at auto dealerships located less than 200 meters (about 220 yards) from each other, the Tamaulipas Attorney General's Office and the Public Safety Secretariat said in a statement.

One of the grenades set a vehicle on display outside the Renault dealership on fire.

The second grenade damaged the exterior of the Volkswagen dealership a short distance away.

Three people at the Volkswagen dealership suffered minor wounds and were taken to a hospital for treatment.

The prosecutor on duty and police went to the scene and opened an investigation, informing the federal Attorney General's Office of the incident.

Army troops, Federal Police officers and emergency services personnel all responded to the attacks, cordoning off the crime scenes, officials said.

Tamaulipas and neighboring Nuevo Leon state have been rocked by a wave of violence unleashed by drug traffickers battling for control of smuggling routes into the United States.

The army is carrying out "Operation Northeast" in Tamaulipas, Nuevo Leon, Coahuila and San Luis Potosi states in an effort to weaken the drug cartels that operate in the region.

The Gulf drug cartel has been waging a war in northeastern Mexico against Los Zetas, a band of army special forces deserters turned hired guns and drug traffickers. EFE