The Revolutionary Armed Forces of Colombia has established undercover cells abroad in 17 countries, a Spanish newspaper says, quoting from documents found on the computer of Raul Reyes, a slain commander of the anti-government group.
El Pais said on Sunday that Farc was using a strategy involving setting up legal organisations.
The report said that Farc was the central force behind a leftist group called the Bolivian Continental Co-ordinator, which had branches in 17 countries including Germany and Switzerland.
Farc was using these and other forums to set up support groups and underground cells, the daily said.
A diplomatic offensive seeking support throughout Latin America had found a providential friend in Hugo Chavez, the Venezuelan president, El Pais said in the latest of a series accusing Chavez of secretly helping FARC.
The daily had claimed on Saturday that Chavez allegedly tried to arm Farc with help from the former Soviet republic of Belarus.
El Pais quoted a message in a February 8 email from Ivan Marquez, a Farc leader, saying Chavez had considered with Belarus authorities the possibility of providing weapons to Farc.
The email was alleged to have been found in the files of a seized computer of Reyes, who was Farc's second-in-command when he was killed in March in Ecuador during a Colombian cross-border military raid, El Pais said.
Venezuela says the computer files are not genuine.
The El Pais
report said the Farc's diplomatic strategy was launched in 2002 at a difficult time for the fighters because they had just been added to a European Union list of terrorist organisations.
El Pais reported last December that Venezuela had become a safe haven for Farc, currently harbouring several camps on its territory.
Venezuela has denied the charge.
The Wall Street Journal had reported on Friday that US intelligence officials believed the seized computer files showing strong connections between Chavez and Farc, were authentic.
The files described meetings between Farc commanders and senior Venezuelan officials including Chavez himself, the Journal said, based on its review of more than 100 documents allegedly seized from Reyes's computer.