MEXICO CITY -- One of the top three leaders of Mexico's most powerful drug cartel, Ignacio "Nacho" Coronel," was killed Thursday in a gunbattle with soldiers, the Mexican army announced.

The death of Coronel, 56, is the biggest strike yet against Sinaloa cartel led by Joaquin "El Chapo" Guzman -- Mexico's top drug lord -- since President Felipe Calderon launched a military offensive against drug traffickers in late 2006.

According to the FBI, which offered a $5 million reward for Coronel, he was believed to be "the forerunner in producing massive amounts of methamphetamine in clandestine laboratories in Mexico, then smuggling it into the U.S."

Gen. Edgar Ruiz Villegas said an army raid was closing in one of Coronel's safehouses in an upscale suburb of the western city of Guadalajara, when the drug lord opened fire on soldiers.

"Nacho Coronel tried to escape, and fired on military personnel, killing one soldier and wounding another," Ruiz Villegas said at a news conference in Mexico City. "Responding to the attack, this 'capo' died."