|The president ordered a brigade of marines to Tumaco to re-inforce security in September [GALLO/GETTY]
Ten Colombian soldiers have been killed and six others wounded in an attack near the border with Ecuador that the military blamed on leftist fighters.
Colombia's army said members of the Revolutionary Armed Forces of Colombia (FARC) detonated explosives as two military vehicles travelled in the southern province of Narino.
Narino, near the border with Ecuador, is known for drug production and trafficking and is one of the most violent areas in Colombia.
"We suffered a hit early this morning from a FARC squad," General Alejandro Navas, commander of the Colombian military, told reporters on Friday.
Navas said "tactical errors'' led to the deaths in the apparent ambush.
The dead were part of a 27-man platoon on patrol near an African palm plantation. Among those killed were a lieutenant and nine enlisted men. The six injured soldiers were taken to hospital for treatment, a military official said.
Leftist fighters, criminal gangs and former right-wing armed groups are all active in Narino and engaged in an ongoing battle over control of the lucrative coastal Pacific drug-trafficking routes.
Narino Governor Antonio Navarro Wolf said the attack "had been prepared for several days" by the FARC fighters.
In late September, Colombian President Juan Manuel Santos ordered a brigade of marines to Tumaco, located 1,200km southwest of Bogota, to help re-inforce regional security.
The Colombian government has been battling the estimated 8,000 fighters among the ranks of South America's oldest rebel movement since 1964.
Friday's incident was the highest death toll for Colombia's security forces in a single attack since 14 police were killed in September 2010 while riding in a convoy in the southern state of Caqueta, a traditional FARC stronghold.
Several hundred security force members are killed annually in Colombia's low-level conflict.
Leftist fighters of the FARC and National Liberation Army also traditionally stage attacks before elections.
Colombians on October 30 will choose governors, mayors and city councilors nationwide in a campaign already marked by election violence.
At least 41 candidates have been killed in pre-election violence, the independent Electoral Observer Mission said.
Active since the 1960s, the Marxist-inspired FARC have been severely weakened since a military offensive launched in 2002 but remain capable of staging attacks, in part due to cash raised through their involvement in the illegal drugs trade.