Four transit police officers have been killed this week in the area around Monterrey, the capital of the northern Mexican state of Nuevo Leon, a state Security Council official said.
Gunmen traveling in several vehicles attacked an officer on Monday with AR-15 assault rifles in Guadalupe, a city in the Monterrey metropolitan area, killing him, state security council spokesman Jorge Domene said.
The same gunmen killed two other officers a few minutes later while they were riding in their patrol car in Guadalupe, Domene said.
A transit police officer was killed on Sunday afternoon in Valle Verde, a neighborhood in Monterrey.
A total of 15 transit police officers have been killed this year by gunmen working for drug cartels and other organized crime groups.
The Monterrey city government has provided officers with bullet-proof vests in an effort to protect them.
Nuevo Leon and neighboring Tamaulipas state have been rocked by a wave of violence unleashed by drug traffickers battling for control of smuggling routes into the United States.
More than 1,000 people, including about 80 police officers, have died in the violence in Nuevo Leon in the past year.
The violence has intensified in the two border states since the appearance in Monterrey in February 2010 of giant banners heralding an alliance of the Gulf, Sinaloa and La Familia drug cartels against Los Zetas.
Heriberto Lazcano Lazcano, known as “El Lazca,” deserted from the Mexican army in 1999 and formed Los Zetas with three other soldiers, all members of an elite special operations unit, becoming the armed wing of the Gulf drug cartel.
After several years on the payroll of the Gulf cartel, Los Zetas went into the drug business on their own account and now control several lucrative territories.
The cartels arrayed against Los Zetas blame the group’s involvement in kidnappings, armed robbery and extortion for discrediting “true drug traffickers” in the eyes of ordinary Mexicans willing to tolerate the illicit trade as long as the gangs stuck to their own unwritten rule against harming innocents.
A total of 15,270 people died in drug-related violence in Mexico last year, and more than 36,000 people have died since President Felipe Calderon declared war on the country’s cartels shortly after taking office in December 2006.
Calderon has deployed tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.
The anti-drug operation, however, has failed to put a dent in the violence due, according to experts, to drug cartels’ ability to buy off the police and even high-ranking officials.