NUEVO LAREDO (AFP) - A shoot-out between rival gangs left 18 people dead Monday in Mexico's Tamaulipas state, amid a surge in deadly drug-related crime, the state govt said. The govt meanwhile announced the arrests of two alleged gang bosses and fresh charges against the scion of a major drug trafficking family, but previous arrests and killings have done little to stem the violence. More than 34,600 people have been killed in clashes between rival cartels and security operations since Mexican President Felipe Calderon launched a massive military crackdown on the drug gangs in 2006. Early on Monday, "there was a confrontation between two crime groups in the Abasolo town center, in which 18 people died," the Tamaulipas state government said in a brief statement on its website. Tamaulipas, on the border with the US state of Texas, has been rocked in the past year by the drug violence surging across Mexico. Locally, the bloodshed is blamed on clashes between the once-allied Gulf and Zetas cartels. The state has been the scene of horrifying killings, including last August, when a mass grave containing the bodies of 72 people, believed to be Central American migrants, was found on a local ranch. The government said Monday that police had nabbed two alleged drug bosses, including one who told authorities that some cartels had entered into a non-aggression pact. Federal police arrested Marcos Carmona, alias "El Cabrito," an alleged leader of the Zetas cartel in Oaxaca state, the Public Safety Ministry said. Carmona told authorities that the Zetas, which is run by former elite soldiers, "have a non-aggression and cooperation agreement" with the Juarez, Tijuana and Beltran Leyva brothers' cartels. Those four groups are among the seven main cartels blamed for the staggering bloodshed. The ministry also said authorities had arrested Benjamin Flores Reyes, alias "El Padrino," believed to be a key member of the Independent Acapulco Cartel. Mexican authorities have also pressed fresh charges of money laundering against Vicente Carrillo Leyva, son of the late famed drug lord Amado Carrillo Fuentes, after Leyva was previously acquitted of drugs charges. Fuentes led the powerful Juarez Cartel until his death in 1997. The cartel, currently led by Vicente Carrillo Fuentes, has been fighting with the Pacific coast-based Sinaloa cartel for control of the key drug route into the neighboring US city of El Paso for more than three years. Previous blows to the gangs' leadership have done little to stem the violence, as the cartels have battled over lucrative trade routes north to the United States, where demand for illegal drugs remains high.