BOGOTA (Reuters) – Colombian rebels have obtained rockets that Venezuela bought in Europe, the government in Bogota said yesterday, an accusation that could worsen already tense relations between the neighbouring countries.

Colombian Vice President Francisco Santos said the government is investigating how the anti-tank weapons found their way to the Revolutionary Armed Forces of Colombia, or FARC.

“In several operations we have been able to capture arsenals of the FARC. We have found heavy weapons, including anti-tank weapons that a European country sold to Venezuela and that ended up in the hands of the FARC,” Santos told local radio. Venezuelan Interior Minister Tareck El Aissami said the accusation is not true, calling Santos’s statement “an aggression.”

Colombian weekly news magazine Semana said on Sunday that Swedish missiles that were sold to the Venezuelan government have been discovered in FARC camps.

The guerrillas have been fighting for a socialist revolution since the 1960s and are labeled terrorists by Washington.