MEXICO CITY – Four gunmen died in a battle with Mexican soldiers near a city just across the border from Brownsville, Texas, the defense department said.

Assailants traveling in three vehicles opened fire Thursday on a contingent of soldiers headed toward Matamoros on Highway 99 in the northeastern state of Tamaulipas, the department said.

The troops returned fire, killing four of the attackers, and seized one of the vehicles, a stolen SUV found to contain four rifles and 730 rounds of ammunition.

Some 30 people have died in Tamaulipas since last Sunday amid a wave of attacks attributed to a feud between the Gulf drug cartel and former allies “Los Zetas,” a band of Mexican special forces deserters turned killers-for-hire.

The mayhem prompted the temporary closure of the U.S. Consulate in Reynosa, Tamaulipas, which lies across the Rio Grande from McAllen, Texas.

President Felipe Calderon, inaugurated in December 2006 for a six-year term, has deployed 50,000 soldiers and 20,000 federal police to a dozen Mexican states to battle the drug gangs.

His government has scored some high-profile victories against the cartels, including the killing of kingpin Arturo Beltran Leyva in December.

But drug-related carnage has only accelerated since Calderon militarized the struggle against organized crime, with more than 17,000 killings since the president took office.

So far this year, drug-related violence has claimed the lives of more than 1,400 people, Mexico City daily El Universal says. EFE