The Chechen leader, Aslan Maskhadov, has warned that his forces are starting an all-out guerrilla war against Russian troops.

Earlier Russia acknowledged that its forces in the republic were facing strong resistance from rebels.

Chechen officials said the fighting was the fiercest since rebels had abandoned the capital, Grozny, last week and retreated to the south.

Russian forces are now carrying out heavy strikes as part of efforts to flush them out.

A BBC correspondent who has travelled inside Chechnya says the landscape bears the scars of the vicious battles that have taken place.

In one village he said the sky was darkened by the smoke of a burning oil refinery, buildings were shattered and the people humiliated.

From the newsroom of the BBC World Service