MEXICO CITY (Reuters) - Ignacio "Nacho" Coronel, a leading Mexican drug trafficker, was killed in a clash with state security forces, local media reported on Thursday.

The reports, if true, would mark a major coup for Mexican President Felipe Calderon's war against increasingly bold drug cartels that have parts of Mexico under siege.

Coronel, who has been indicted in the United States, is a senior member of the powerful Sinaloa cartel, based in northwestern Mexico, and a top lieutenant of its leader, Mexico's most-wanted fugitive, Joaquin "Shorty" Guzman.

Reforma, a major Mexican newspaper, reported that Coronel, who was known as the "King of Ice" for his multimillion-dollar methamphetamine trafficking business, died as shots were fired during an army raid in a wealthy residential area in the town of Zapopan in central Mexico.

Other Mexican media also reported his death.

The killing could be a boost for Calderon, who launched a military campaign against drug gangs when he took power in late 2006. But the conservative leader's image has been stained by spiraling violence across the country and critics note that he has failed to capture any leading drug bosses this year.

More than 26,000 people have died in drug violence across Mexico over the past 3-1/2 years, making cartel activity in Mexico a growing worry for the administration of U.S. President Barack Obama, some global investors and foreign tourists.

Mexican security forces shot dead top drug lord Arturo Beltran Leyva in December in Calderon's biggest blow to date in his war on drugs.

(Reporting by Mexico City newsroom; Editing by Eric Walsh)