MEXICO CITY — A car bomb exploded early Tuesday outside the home of the top security official in the state of Tamaulipas, a region that borders Texas and has been a violent battleground for drug cartels. Two police agents were killed and seven police and civilians injured.

It was the second such attack in a week in Tamaulipas.

Tuesday’s explosion occurred in the state capital of Ciudad Victoria. On Friday, suspected drug traffickers set off a car bomb near City Hall in Nuevo Laredo, a city that sits across the border from Laredo, Texas. Seven passersby were injured in the Nuevo Laredo blast.

The Ciudad Victoria bomb reportedly was detonated by a cellphone in a car parked in front of the home of Rafael Lomeli Martinez, public security secretary for the state, according to Morelos Canseco, state interior secretary. Lomeli, who had just arrived home, was not injured, but two policemen from his security detail were killed and four injured, one gravely, Canseco said. Three people passing by were also injured.

Tamaulipas has been torn apart by battles between the notorious Zetas paramilitary force, fighting its one-time patron, the Gulf Cartel, which is now believed allied with the powerful Sinaloa cartel. A former governor of Tamaulipas is under investigation for alleged ties to cartels, and in 2010 a candidate expected to be elected governor of Tamaulipas was assassinated in broad daylight on the eve of the vote.

Though still less common than other weapons, the use of car bombs has increased in Mexico’s drug war, primarily in Tamaulipas.

Sign up for our daily newsletter

Get the best of The Post and Courier, handpicked and delivered to your inbox every morning.