Though initial suspicion centred around them, the Revolutionary Armed Forces of Colombia (FARC) claimed the Colombian military intelligence was to be blamed instead.
"It is false that our guerrilla units are responsible for kidnapping the eight tourists," a statement from the 17,000-member strong underground outfit said.
Four Israelis, two Britons, a Spaniard and a German were abducted last Friday. Witnesses said they were marched away into the jungles of the Sierra Nevada mountains.
Colombian authorities say FARC kidnaps hundreds of people every year for ransom to fund its insurgency.
But in its statement, FARC accused the authorities of being behind the latest abductions.
"The terrorist operations of the state against the tourists in the Sierra Nevada…are carried out by Colombian military intelligence, with the goal of showing results to the president with a staged rescue," it said.
"It is false that our guerrilla units are responsible for kidnapping the eight tourists"
The Colombian government, however, is certain that FARC is responsible and has sent 2,000 soldiers and police, backed by Black Hawk helicopters, to hunt for the hostages.
The remote northern mountains from where the tourists were kidnapped, are home to multiple guerilla armies.
Right wing paramilitary death squads, paid to kill the rebels and their sympathizers, also operate in the region and are regularly accused of kidnapping.
More than 1,000 people have been kidnapped so far this year in Colombia.
President Alvaro Uribe, whose father was killed by FARC rebels, said every effort was being made to rescue the hostages.
The abducted tourists had ignored a US travel warning against visiting the region to see the 2,500-year old ruins of an ancient Indian city.