(CNN) -- Leftist guerrillas with Revolutionary Armed Forces of Colombia (FARC) offered Venezuela's intelligence agency "training in urban terrorism involving targeted killings" and suggested they were willing to assassinate opponents of Venezuelan President Hugo Chavez, according to a new study of the Colombian rebels' records.
At one point, Chavez even offered to provide FARC with $300 million and weapons, but those deals apparently fell through, according to a trove of e-mails and documents seized from a key FARC leader.
The new analysis, which was immediately disputed by Venezuelan officials, was provided by the London-based International Institute for Strategic Studies, which on Tuesday released a book-length dossier that examines in detail the Colombian rebels' relationship with Venezuela and Ecuador.
The institute spent two years researching 30 years' worth of strategic documents and recent e-mails belonging to FARC leader Luis Edgar Devía Silva, whose nom de guerre was Raul Reyes. He was killed in a 2008 raid, leaving behind the digital records.
FARC is "Latin America's oldest, largest, most capable, and best-equipped insurgency of Marxist origin -- although it only nominally fights in support of Marxist goals today," according to the National Counterterrorism Center. The United States and European Union consider FARC a terrorist group.
FARC gained momentum in Venezuela after Lt. Col. Hugo Chavez became president in 1999. While espousing neutrality in the conflict between FARC and the Colombian government, Chavez's government funded FARC's office in Caracas and gave it access to Venezuela's intelligence services, the study said.
"Following the 2002 coup which briefly removed Chavez from power...," the report said, "FARC also responded to requests from (Venezuela's intelligence service) to provide training in urban terrorism involving targeted killings and the use of explosives.
"Furthermore, the archive offers tantalizing but ultimately unproven suggestions that FARC may have undertaken assassinations of Chavez's political opponents on behalf of the Venezuelan state," the institute said.
In a heated response, the Venezuelan Embassy in Washington called the documents unreliable, and dismissed the credibility of the British institute's book, which is called "The FARC Files: Venezuela, Ecuador and the Secret Archive of Raul Reyes."
Colombian officials told CNN Tuesday that they weren't going to comment on the institute's findings.
In a statement, Venezuelan diplomats said the report contained "basic inaccuracies" and added that the Colombian Supreme Court has even called into question the rebel group's documents, not allowing them to be used in the prosecution against Colombian officials.
"The embassy expressed its surprise and concern at the IISS' decision to use documents whose handling by the Colombian authorities has been said by international police organization Interpol to 'not conform to internationally recognized principles for the ordinary handling of electronic evidence by law enforcement,' " the Venezuelan statement said.
"Given these flaws, the embassy said that this brings into question the quality of the rest of the report," the statement continued. "It has also warned that this could become part of an aggressive propaganda tool against Venezuela to undermine progress in the region, precisely at a time when relations between Venezuela and Colombia have reached a level of stable cooperation and friendly dialogue."
In an interview with CNN en Español, Nigel Inkster, a director of the institute who authored a summary of the study, said the relationship between Chavez and FARC was "quite complicated."
For Chavez, "the relationship was to set up a strategic capacity that could be very useful in certain circumstances, but it also posed many domestic and international problems that limited his ability to use FARC," Inkster told CNN. "Chavez was very willing to sacrifice the interest of FARC when it suited him."
In 2004, Chavez suspended his ties with FARC for 18 months after the rebels angered and embarrassed him, the institute said.
But by 2006, as Venezuelan was enriched by high oil prices, Chavez viewed FARC as a strategic ally in his government's disputes with the United States.
"Several meetings took place with senior members of the FARC leadership," the institute study said. "Chavez committed to helping the group achieve political legitimacy, formally reaffirmed FARC's entitlement to use Venezuelan territory along the Colombian border and, critically, offered to provide FARC with US $300 million, with $50 million to be made immediately available. Various options were also explored for providing FARC with the kind of weaponry."
But at the time of Reyes' death, those deals never apparently occurred, the study said.
The institute also found that FARC began establishing strongholds in Ecuador's border regions next to Colombia in the 1990s, where the rebels produced and sold cocaine for income.
Unlike the redoubts it enjoyed in Colombia, FARC found Ecuador "downright hostile" at first, but as Ecuadorian politics moved left, FARC enjoyed better ties and "was successful in fomenting discord between Ecuador and Colombia," the study said.
In 2006, FARC contributed about $400,000 to the campaign of successful Ecuadorian presidential candidate Rafael Correa -- with $100,000 apparently directly from the rebel group and $300,000 more from its allies, the report alleged. Inkster told CNN that those allies were drug traffickers.
"Correa almost certainly approved the use of these funds in his campaign, but this did not translate into a policy of state support for the insurgents during the brief period between Correa's inauguration and Reyes's death," the study said. "Although the death of Reyes provoked a serious breach in relations between Colombia and Ecuador -- ironically a key FARC strategic objective -- it also interrupted FARC's burgeoning relationship with Quito. There is no evidence that the relationship has since prospered."
In an interview with the Spanish-language EFE news service, a member of President Correa's administration, deputy foreign minister Kintto Lucas, called the alleged FARC campaign contributions "totally false" and dismissed the credibility of FARC's computer records.
"We always said we did not recognize the hard drives. We do not know if they really are real or invented," Lucas told EFE. He said that a broken chain of custody for the records could have allowed any intelligence agency to invent the information.
"We will not recognize any information on these because they have no truth," Lucas told EFE.
The institute said the FARC has now fallen "to a low ebb" following Colombia's security crackdowns through the countryside where the rebels have been based. The guerrillas are suffering desertions, and Colombia's intelligence apparatus has neutralized rebel leaders.
But Colombia's abject poverty, land ownership problems and the dilemma of what to do with former paramilitaries make the country "fragile," the institute said.
"Colombia's security forces continue to clash with FARC, and to suffer casualties, on an almost daily basis," the study said. "As long as FARC continues to benefit from a degree of cross-border sanctuary and support, Colombia's development efforts will remain under threat."
CNN's Krecyte Villarreal contributed to this report.