Colombia's army on Saturday said FARC guerrillas opened fire on its troops with homemade mortars from across Ecuador's border in the latest incident to test frayed relations between the Andean neighbours.
Ecuadorean President Rafael Correa broke off diplomatic ties with Colombia last month during a regional crisis when Colombian troops killed a top Farc commander in an attack on a base hidden over the border inside Ecuadorean territory.
Army Commander General Mario Montoya said rebels had launched gas cylinder mortars from the Ecuadorean side of the frontier to attack Colombian soldiers in southern Putumayo province, where armed groups often grow coca to make cocaine.
"These bandits from Farc have once again fired… cylinders filled with explosives from Ecuadorean territory against Colombian troops who were providing security to an oil company," Montoya told reporters.
One soldier was wounded in the attack, he said.
Border incidents and a flurry of accusations between Bogota and Quito have kept tensions high between the two countries since March when Colombian troops attacked a Farc base over the border to kill rebel chief Raul Reyes.
Colombia's President Alvaro Uribe said the attack was legitimate because Bogota had warned Ecuadorean officials repeatedly about Reyes's camp and received no help. But Ecuador and Venezuela reacted by sending troops to their frontiers with Colombia and cutting ties with Bogota.
Colombian authorities say computers found at Reyes camp in Ecuador contained files revealing close Farc ties to Venezuelan President Hugo Chavez and Correa, but both leaders dismiss those charges as part of a smear campaign against them by Uribe's government.
The crisis has underscored political divisions in the Andes where Correa and Chavez promote a leftist agendas and oppose US policies while Uribe is one of Washington's staunchest allies in Latin America.
Colombia's conflict has eased under Uribe, who has received billions of dollars in US aid to help counter the insurgency. The Farc, labelled a cocaine-trafficking terrorist group by US and EU officials, has been pushed back into more remote regions.