Mexico City ? Mexico’s extradition of four reputed drug lords drew praise from the U.S. attorney general on Saturday and signaled its new determination to keep traffickers from running their cartels from inside prison walls.

U.S. Attorney General Alberto Gonzales said the Friday extraditions were “unprecedented in their scope and importance.”

Osiel Cardenas, the alleged Gulf cartel leader who was believed to be running his gang from prison in Mexico, was sent north late Friday along with 14 others wanted by the U.S. after their appeals against extradition ran out, the office of Mexico’s attorney general said.

“Never before has the United States received from Mexico such a large number of major drug defendants and other criminals for prosecution in this country,” Gonzales said in a statement on Saturday.

The Mexican attorney general’s office released photos showing the balding Cardenas being escorted onto a plane bound for the United States in handcuffs, surrounded by U.S. and Mexican agents.

The office said the extraditions were also aimed in part at cracking down on turf battles between Mexican drug cartels, which have cost hundreds of lives in recent months in states like Michoacan, Guerrero, Baja California and Sinaloa. The government has recently sent thousands of soldiers and police to try to stem the drug-fueled violence.

“This changes the rules, as far drug traffickers’ impunity and the potential punishment they face,” said Oscar Aguilar, a political science professor at Mexico City’s Iberoamerican University. “Before, the capos could say, ‘Well, if they ever do catch me, I’ll be in Mexico, my family and associates can visit me whenever they want, and I can keep running the business'” from prison.

Federal agents detain two men for allegedly selling drugs during part of a new anti-drug operation backed up with military help in Acapulco, Mexico, on Saturday. Since taking office in December, Mexican President Felipe Calderon has sent thousands of troops to help the fight against drug cartels and now has extradited top Gulf cartel leader Osiel Cardenas and three other high-profile drug barons to face charges in the United States.

Mexican officials have said that Cardenas and top members of the Tijuana cartel had forged an alliance while locked up at a maximum-security prison just west of Mexico City, where they organized to fight turf wars against rival drug lords.

Authorities also said Cardenas sought to control that prison and other jails through gangs of inmates, and may have organized killings both inside and outside prison. Authorities say he ran his cartel by passing messages to lawyers representing him and dozens of associates.

The United States once offered a $2 million reward for Cardenas before his 2003 arrest. In 1999, U.S. officials said Cardenas held two U.S. agents at gunpoint in their car in a Mexican border city, then let them go saying: “You gringos, this is my territory. You can’t control it, so get the hell out of here.”

In the past, Mexico has been reluctant to extradite major Mexican drug lords to the U.S., arguing they should face justice here first. They also refused to send anyone to the U.S. who would face the death penalty, which is illegal in Mexico.

But that attitude changed under former President Vicente Fox, who last September promised to extradite “all of those who have pending matters with U.S. justice.” Fox extradited a record 63 alleged criminals to the U.S. in 2006, including the suspected drug kingpin Francisco Rafael Arellano Felix.

In addition to Cardenas, Mexico on Friday extradited Ismael and Gilberto Higuera Guerrero, brothers and former chiefs in the Arellano-Felix cartel in Tijuana and Mexicali; and Hector Palma Salazar, a former leader in the Sinaloa cartel led by Joaquin “El Chapo” Guzman.