According to the president, the execution “could be the cruelest thing we have seen in a long time.”
“They had them as hostages, chained, and when they found themselves confronted with the security forces showed no restraint in assassinate them in cold blood,” Santos added.
Defense Minister Juan Carlos Pinzon said government troops, who had been in the area for 45 days chasing rebels, had intelligence that the guerrillas might be holding police and soldiers as captives.
No official explained the nature and reliability of that intelligence or whether the four died in a failed rescue mission.
All four men were killed execution-style, three with shots to the head and one with two shots to the back, Santos told a community meeting in central Colombia.
Neither the president nor Pinzon, who was first to announce the deaths and did not take questions from reporters, said whether the four were believed to have been killed Saturday. Pinzon said the bodies were found together, with chains near them.
Santos sent his condolences to the family members of the hostages, who spent the last 12 years of their lives held captive by the rebels in the Colombian jungle.
Additionally, Santos sent his condolences to the armed forces, “because I know the pain it inflicts on our military and police.”
The killing of the four prisoners has been widely condemned by Colombian politics.
Former Senator Piedad Cordoba, who had brokered the release of hostages in the past, called the murders “a heavy blow” against peace.
In an interview with Caracol Radio. Cordoba said the FARC’s action “obliges us to work ethically for peace and think teh way out is not through war.”
Interior Minister German Vargas Lleras called the “miserable assassins” on his Twitter account.
“What pain, the killing of our policemen and soldiers, tied with chains,” said former President Alvaro Uribe in a statement in which he expressed solidarity with the government and armed forces.
Family members of the executed members of the security forces fiercely criticized the government for its attempt to use force to free the prisoners.
“It is government policy to have officials for the FARC to kill. The army is guilty,” said the father of one of the killed policemen. According to Marleny Orjuela, who represents family members of captive policemen and soldiers, rescuing hostages with “blood and fire is useless.”
The four prisoners were part of a group of 21 held by the guerrillas as political leverage and executed when armed forces were trying to rescue their colleagues.