Three bomb explosions have cut off north-east India from the rest of the country, by severely damaging road and rail bridges in the narrow corridor of land which links the state of West Bengal with Assam.

No group has yet admitted responsibility for the attacks, but Indian intelligence officials say they suspect militants fighting for a separate homeland in western Assam for the Bodo tribe.

The BBC North East India correspondent says Delhi recently made it clear to Bodo leaders that a Bodo state was not possible and this might have spurred the separatists to renewed action.