Leftist guerrillas attacked a vehicle carrying Colombian police on Monday, setting off a battle that killed seven officers and 25 rebels, authorities said, Reuters reported.
A local rebel commander known as "El Enano," or The Midget, appeared to be among the guerrillas killed in the fighting near the town of Buenos Aires in Cauca province, police said.
Government security forces continued battling members of the Revolutionary Armed Forces of Colombia, known as FARC, into Monday night around Buenos Aires, authorities said.
Thousands of people are killed, displaced or maimed by landmines every year in Colombia's conflict, which started with the birth of the FARC in the 1960s.
The cocaine-financed rebels say they are fighting for socialism in the Andean country. President Alvaro Uribe is popular for his U.S.-backed crackdown on the guerrillas.