Colombian President Juan Manuel Santos has warned the country's leftist rebels against resuming violent guerrilla operations, saying the army and police were ready to respond to their attacks.

The warning came as a unilateral ceasefire announced by the Revolutionary Armed Forces of Colombia (FARC) in November to facilitate peace talks with the government was set to expire on Sunday.

"We have to tell the Colombian people that we are ready for this," Santos declared Saturday, speaking in the town of Padilla, in the southeast of the country.

"Terrorist acts are cowardly acts because they don't fight against soldiers or members of the police force," he continued. "They inflict damage on civil society."

The president said Colombian security forces had already detected what he described as "some attempts to perpetrate acts of terrorism."

And he urged the FARC to refrain from new operations, saying "they know perfectly well what they need to do after Sunday."

On Friday, the police announced they had foiled a plot by the FARC to bomb police and military facilities in the capital Bogota after the end of the truce.

Officials said a raid in the town of La Palma, some 150 kilometers from Bogota, had uncovered 250 kilograms of explosives, a detonating cord and six grenades, National Police Director Jose Leon said.

AFP