Colombia's feared death-squad leader, Carlos Castaño, is believed to have been killed in a guerrilla attack on his mountain hideout.

Guerrillas from the Revolutionary Armed Forces of Colombia (FARC) say he was killed in fighting when they overran his mountain stronghold in the north of Colombia.

Mr Castaño is the leader of the largest right-wing paramilitary group in Colombia, the United Self-defence Forces of Cordoba and Uraba.

A spokesman for the group said their leader's camp had been destroyed and that Mr Castaño was missing but could not confirm whether he had been killed.

Mr Castaño's death squads have been conducting a campaign against the country's estimated 20,000 left-wing guerrillas.

The standard operating procedure for his death squads is to arrive in villages and guerrilla strongholds with a list containing names of those accused of being guerrilla activists or sympathisers.

Everyone the paramilitaries finds from the list is immediately shot. The message is simple and has been frighteningly effective.

Last year the paramilitaries were guilty of the vast majority of the 185 massacres and political killings that left more than 2,100 people dead, according to the figures compiled by Human Rights Watch.

But Mr Castaño has always been unapologetic about his methods.

In a recent interview, he told reporters that he and his men violated human rights but that was the nature of the war he was fighting.

Despite the fact that Mr Castaño has had a $1m bounty on his head for over a year and is wanted by the State on a list of charges, neither the Colombian police nor the army have apprehended him.