Russia wants to prevent the conflict spreading

Reports say a remote-controlled landmine exploded under one of the trucks in the convoy.

The attack took place on Tuesday evening near the village of Galashki on the border with Chechnya.

It came as pro-Moscow Chechen leader Ahmad Kadyrov confirmed he would stand as an independent in presidential elections in the republic in October.

The election is part of efforts by Moscow to restore normality to the war-torn region, but is not recognised as legitimate by the rebels.

'No second Chechnya'

Correspondents say the long and bitter conflict for independence in Chechnya occasionally spills over into neighbouring republics where many Chechens have gone to escape the fighting.

Last September, Russian troops fought a fierce battle with around 180 rebels in the same area of Ingushetia. One Russian helicopter was shot down.

However, Ingush president Murat Zyazikov said there was no reason for troops based in Chechnya to move to his republic following the latest incident.

"It is true that there are forces that want want to expand the conflict," he said. "They exist in Chechnya and they exist abroad. But there will be no second Chechnya in Ingushetia. The situation is under control."

There are close links between the two republics, which were combined as a single entity within the Russian Federation until 1991.