Bogota - A Colombian military commander has accused the nation's largest rebel army of planting a powerful bomb that tore through the offices of a military anti-kidnapping squad, killing nine people.

Although no group had claimed responsibility for the attack, General Eduardo Herrera, commander of the army's 4th Brigade based in Medellin, told reporters that he blamed the leftist Revolutionary Armed Forces of Colombia, or FARC.

But in an interview on Friday night, senior FARC commander Raul Reyes said he had no knowledge of the attack. "We regret the deaths," said Reyes, a member of the rebel group's seven-man ruling junta.

The attack occurred on Friday afternoon, when a truck packed with 90 kilograms of explosives went off in a residential neighborhood of Medellin, 250 kilometers northwest of Bogota, said Medellin police spokesman Haten Dasuki.

A female passer-by, two officials from the federal prosecutor's office and an agent from the state security police were among the dead, officials said.

Thirty people were injured in the explosion, which leveled the offices of the anti-kidnapping squad, Gaula. Colombia has the world's highest kidnapping rate, with 2 216 people abducted last year, according to the Pais Libre foundation.

"It was a powerful bomb, like the ones that went off during Pablo Escobar's time," Dasuki said.

During the 1980s, Colombia's second-largest city was regularly rocked by bomb explosions, as the now-defunct Medellin cocaine cartel led by Pablo Escobar waged a terrorist campaign against the government.

The FARC has been engaged in peace talks with the government of President Andres Pastrana since January, but, as yet, there is no cease-fire in effect.

On Friday, government and rebel negotiators met in the rural southern village of La Tunia but failed to reach an agreement on the role for international monitors in peace talks to end Colombia's 35-year conflict.

Presidential peace envoy Victor G Ricardo said the guerrillas were refusing to accept the appointment of an international commission to accompany the talks and monitor a massive region the government has ceded to the FARC.

Pastrana had pulled troops and police from the 42 000-kilometer southern region, which includes La Tunia, as a concession to entice the rebels to the negotiating table.

It was the third time in less than a month that the two sides have met and were unable to overcome the dispute many observers feel could torpedo the entire peace process.

Local television images showed the shattered facades of at least a half dozen houses, and vehicles flipped onto their sides by the blast, the second explosion in Medellin in less than two weeks. Ambulances sped to and from the scene and soldiers guarded the ruins, where two of the bodies lay covered with white sheets.

On July 19, a Renault sedan packed with explosives was set off by suspected leftist rebels in front of the offices of a large cement company, destroying its glass facade. There were no deaths, but a night watchman was injured. - Sapa-AP