The surprise accusation was made in a statement read last night to a radio station by Nicolas Rodriguez, top commander of the 15,000-member National Liberation Army, or ELN, Colombia's second-largest guerrilla group.

``We assume the responsibility for the blowing up of the pipeline, but our conscience is clear because the criminals are not within our ranks,'' the rebel chief said, breaking silence on the incident. Government officials had suspected the ELN in the blast, and were demanding that they clarify their role.

There was no immediate response from President Andres Pastrana, who had been careful in statements not to directly accuse the rebels who have a long history of attacking oil pipelines.

Colombia's armed forces chief denied that his men were involved.

``Our troops were not inthe area. They only arrived later to help the population,'' said Gen Fernando Tapias in a television interview last night.

The Ocensa pipeline, a 820 km facility carrying crude from eastern oil fields to Caribbean ports, is jointly owned by the Colombian state oil company Ecopetrol and a consortium including US, French, British and Canadian companies.

The rebels, who have carried out more than 60 pipeline attacks this year, say they are protesting excessive government concessions to foreign oil interests.

In his statement, ELN commander Rodriguez admitted that guerrillas set off an explosion at 2:00 am on Sunday in the vicinity of Machuca, the rural hamlet in central Antioquia state which was devastated by the weekend's blaze.

But Rodriguez said the subsequent fire which raged through the village of gold miners, killing 47 people and injuring 60 more, was set off an hour later, possibly by soldiers at an army base located near where the fire allegedly began.

``The people of this region are wellaware of this type of army behavior,'' Rodriguez said, claiming the military had set fires after other guerrilla pipeline attacks.

The majority of the dead were women and children who were asleep in simple wooden houses when the flames sped through Machuca.

News that Leftist rebels were involved, could poison the atmosphere for peace talks to put an end to Colombia's 34-year civil war. Pastrana is set to begin negotiations on November 7 with the country's other leading guerrilla faction, the revolutionary armed forces of Colombia.

Separate, preliminary peace talks are scheduled to get under way with the ELN in February.