Members of the militant Basque separatist group ETA trained around 100 guerillas from Colombia's rebel FARC group in camps in Venezuela, the Spanish daily El Pais reported Sunday.

According to the newspaper, ETA fighters gave lessons in advanced explosives techniques in at least six Venezuelan camps between 2003 and 2008.

El Pais said the information came from witness statements made by four former FARC members to Spanish police in Bogota last October.

The ABC newspaper in Madrid quoted Spanish police reports saying ETA and FARC first made contact in Cuba in 1993 and held two training camps in 2003.

ETA members learned how to make and use grenades and surface-to-air missiles while FARC fighters were shown techniques for urban guerilla warfare, particularly how to use mobile phones as remote detonators for bombs, ABC said.

Last Monday a Spanish judge charged that ETA and FARC plotted to kill Colombian politicians in Spain, including President Alvaro Uribe, with Venezuelan "governmental cooperation."

This move prompted tension between Madrid and Caracas, and led to the two governments issuing a joint statement stressing their ties in the fight against terrorism.