A top rebel leader was killed by his own chief of security, who gave Colombian troops the leader's severed hand as proof, the defense minister said Friday.

Ivan Rios was the second top rebel killed in a week, a major setback for the Revolutionary Armed Forces of Colombia, the country's largest rebel force.

No top Colombian rebel leader had ever been slain until Raul Reyes was killed Saturday in a cross-border raid by Colombian troops into Ecuador that set off an international diplomatic crisis.

"The FARC has suffered a new, major blow," Defense Minister Juan Manuel Santos told reporters, calling Rios' death "yet another demonstration that the FARC is falling apart."

He said troops launched an operation designed to capture Rios on Feb. 17 after receiving tips that he was in a mountainous area straddling the western Colombian provinces of Caldas and Antioquia, and engaged the guerrillas' outer security ring seven times.

Thursday night, he said, a guerrilla known as Rojas came to the troops with Rios' severed right hand, laptop computer and ID, saying he had killed his boss three days earlier. Rojas handed himself over to the soldiers.

It was unclear what motivated the killing, but Santos said it was to "relieve the military pressure" because the rebels were "surrounded, without supplies and without communication."

The U.S. State Department has a bounty of $5 million for Rios' capture, although the agency's spokesman, Kurtis Cooper, had no comment on whether the reward would be paid out in this case.

Santos said Colombia waited to make the announcement until it had confirmed Rios' identity, which it did Friday.

The military said it was transporting Rios' body to an army base in the western city of Manizales.

Rios, whose real name has been given as Jose Juvenal Velandia and Manuel Jesus Munoz, faced U.S. federal charges of drug smuggling, and was on a U.S. Treasury Department list of terrorists and drug traffickers.

The 46-year-old Rios became known across Colombia as one of the rebels' main negotiators in failed peace talks that ended in 2002. Unlike the FARC's mostly peasant leadership, he was a former university student who engaged journalists and foreign envoys in political and economic discussions.

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