Soldiers killed 12 rebels tasked with providing security to a key Marxist guerrilla commander in central Colombia, while six soldiers died in separate fighting near the border with Venezuela, the military has said.
Those killed included four female guerrilla fighters and eight men who served to protect Guillermo Leon Saenz, who goes by "Alfonso Cano," and is one of the leading figures of the Revolutionary Armed Forces of Colombia (FARC).
The 12 were killed in a middle-of-the-night raid in the central Colombian province of Tolima, the military said on Sunday.
The assault, carried out jointly by Colombia's air force, army and federal police, began around 1:00 am (0600 GMT) in a rural section outside the town of Planadas in the central Colombian mountains.
Among the women killed was Magaly Grannobles, also known as "Marleny Rondon," who headed one of the units responsible for Cano's security.
"This is a major setback for the guerrillas, because this terrorist, who has assassinated about 70 Colombian soldiers and police officers, was very important to Cano," said General Freddy Padilla, commander of Colombia's military forces.
The six soldiers died in combat with the FARC in Arauca, a province bordering Venezuela, the military said later. Four soldiers were wounded.
The clashes in central and eastern Colombia came a day after three separate attacks attributed to the FARC left three police officers, two soldiers and two civilians dead.
The FARC, the country's strongest and oldest guerrilla group has been fighting the government since the 1960s. It now includes some 7,500 to 10,000 fighters, according to estimates.