Colombian FARC rebels killed four military hostages who had been held prisoner for years, Colombia's defence minister said on Saturday.

It was the most violent act by the drug-funded guerrilla group since the armed forces killed its leader and main ideologue, Alfonso Cano, in a raid earlier this month.

They were brutally murdered, Defence Minister Juan Carlos Pinzon told a news conference.

He said the killings took place in the southern jungle region of Caqueta after a firefight in the area between the rebels and members of the armed forces.

Latin America's No. 4 oil producer has been wracked by bloodshed from guerrillas and cocaine barons for decades. But a 2002 security crackdown drastically reduced the violence and brought in billions of dollars in foreign investment.

On Thursday, President Juan Manuel Santos said the Andean nation was nearing the final phase of nearly 50 years of war and that his government would be willing to sit down and talk peace if the guerrillas were serious.

The government has hailed the killing of Cano as the most devastating blow yet against the FARC. The big steps Colombia has made on the security front, however, mask unresolved issues from unequal land distribution and rural poverty to flourishing criminal gangs, and politicians corrupted by drug money.

(Reporting by Luis Jaime Acosta and Nelson Bocanegra; Writing by Daniel Wallis)