At least 10 police officers died and five were injured in an attack by leftist rebels in Colombia, near the Ecuadorian border, the authorities said.
This takes the total number of police and military officers killed by leftist rebels over the past week to 40.
The latest attack by the Revolutionary Armed Forces of Colombia (FARC) took place early Friday in the municipality of San Miguel, in Putumayo province.
San Miguel Mayor Ruperto Benavides said the rebels attacked police officers with bombs near the border bridge.
Colombian President Juan Manuel Santos condemned the attack and vowed to intensify the fight against the rebels.
"They are wrong if they think they will weaken us with this attack. Quite on the contrary, this just charges us with more determination, with more decisiveness, because we are not going to rest a single second until we have complete peace in this country," he said.
Acting police commander Orlando Paez Baron said several rebels also died in the attack, but gave no further details. Officials had lost contact with the survivors, and the fighting was ongoing, so precise figures were unavailable.
During the eight-year presidency of Santos' mentor and predecessor Alvaro Uribe, FARC had been forced into retreat in the four-decade-old conflict that intertwines politics and the drug trade.
In a country where almost half the population lives in poverty, however, the rebels continue to have a substantial amount of power, and the Colombian topology, with its many remote jungle areas, allows them to escape security forces with relative ease.