Alexander Lebed, the former Russian general who negotiated the end of the Chechen war, urged the authorities to send troops to quell the unrest.

BBC: By BBC News Online's Kate Goldberg

Aid workers are needed in the region to provide medical help to tent camps across Dagestan and neighbouring Ingushetia, where some 150, 000 refugees are sheltering from the Chechen war.

BBC: Aid group leaves Dagestan

Russian troops withdrew from Chechnya in 1996 after the first Chechen war, leaving it de-facto independent and largely lawless, but then rolled back three years later following apartment building explosions in Moscow and other cities blamed on the rebels.

NPR: Russia's Chechnya Has Seen Decades Of War, Terror