A similar bombing in a neighbouring republic in August killed 24 people and injured more than 200.

In that attack, a man succeeded in crashing a bomb-laden van through the gates of the police station in Nazran, Ingushetia.

Russia's predominantly Muslim republics in the North Caucasus have seen a sharp rise in violence in the past year, with many of the attacks targeting police and other officials.

Some describe the violence as a civil war between Kremlin-supported local governments and Islamist fighters.