Mexico's federal government announced the deployment of an additional 500 army troops to the northeastern state of Tamaulipas, which has been wracked by turf battles among drug cartels and attacks by the gangs on the civilian population.

The 500 soldiers "will bolster the significant presence of federal forces" already in Tamaulipas, federal security spokesman Alejandro Poire said Thursday without offering details on the total number of military personnel deployed to that state, where 183 bodies were located in 40 clandestine graves in April.

According to the daily Reforma, 8,435 soldiers have been deployed to combat organized crime in the 4th Military Region, which comprises Tamaulipas and the neighboring states of Nuevo Leon and San Luis Potosi, the largest troop presence in the country's 12 Military Regions.

President Felipe Calderon has given the army the lead role in the fight against the country's numerous, well-armed drug cartels, deploying 50,000 soldiers and 20,000 Federal Police to drug-war hot spots, especially in northern Mexico.

Tamaulipas has been wracked by a wave of violence since early 2010, when the Gulf cartel and former allies Los Zetas began a brutal war for control of that region.

Hit men employed by those criminal gangs also have kidnapped people en route to the Mexico-U.S. border - either for ransom or to recruit them as couriers or enforcers - and killed those who resisted.

The one-year deployment of these 500 soldiers to support the Tamaulipas Public Safety Secretariat, which oversees the state police force, was the result of an agreement between the Tamaulipas and federal governments, Poire said.

The federal security spokesman said the deployment is a stopgap measure while the Tamaulipas state police force is purged of corrupt personnel, a process also being carried out in the rest of the country.

State and local police in Mexico are poorly paid and are often confronted with the choice known here as "plomo o plata" (lead or silver): accept a bribe for looking the other way or get killed for refusing.