But in recent days the guerrillas of the group known as the E.P.R., its initials in Spanish, have staged raids in an effort to show that their clandestine army remains intact.

Because the highway passes through areas where guerrillas of the Communist New People's Army have staged attacks in recent months, United States Marines patrolled the road while military helicopters protected the convoy from above.

In recent weeks Chechen guerrillas have staged effective counterattacks and even managed to retake some areas from Russian control.

The army denied that it was involved in the attack and suggested that the guerrillas staged it in an attempt to discredit the Government.

In the short term, there is a good chance that the guerrillas will stage a wave of retaliatory attacks, the experts say.

On Sunday, guerrillas staged brazen attacks that left at least 37 people dead across the country.

Some military experts said on Wednesday that the guerrillas could not have staged such an attack without support from inside Russia's capital.

Yet the violence on Friday, coming during a week when guerrillas staged brazen assaults on Iraqi security forces, demonstrated anew how much work remains before the country will be safe from insurgents.

Two months later, the guerrillas staged coordinated attacks on army and police stations at four sites.

The men were accused by the military of having helped guerrillas stage an ambush that left several soldiers dead.