Four people were killed and six injured in a car bomb in front of a cafe in Russia's volatile North Caucasus region of Dagestan, according to reports quoting local police.
"Three dead and seven injured were taken to hospital, one injured person died on the operating table," a medical source told the Ria-Novosti agency following the attack at Khassaviourt.
Russia is battling an Islamist insurgency in the Caucasus and deadly attacks on government and police officials in Dagestan as well as neighbouring Chechnya and Ingushetia are an almost daily occurrence. Suicide bombings are also becoming increasingly frequent in the Caucasus.
The car bomb followed Monday's suicide bombing at Russia's main airport in which 35 people died.
Unofficial reports have said that bombing was likely planned by militants from the mainly Muslim Northern Caucasus and media have published a photograph said to be the severed head of the suspected bomber.
Monday's blast was Moscow's second attack in less than a year.
Last March, double bombings carried out by two female suicide bombers on the Moscow metro killed 40 and wounded more than 100, marking the deadliest violence in the Russian capital since 2004.