A suicide car bomb attack in a busy marketplace in Russia's Vladikavkaz city, capital of North Ossetia, left at least 15 people dead on Thursday, according to the Itar-Tass news agency.
Around 80 people were injured when the car packed with 40 kg of TNT exploded, according to the interior ministry of the Republic of North Ossetia.
Two people were in the car, which bore the licence plates of the neighbouring predominantly Muslim republic of Ingushetia.
The attack, which occurred on the final day of the Muslim fasting month of Ramadan, damaged numerous buildings in the city and set dozens of cars on fire.
Russian President Dmitry Medvedev and Prime Minister Vladimir Putin condemned the attack and called on the region's Muslim population to help prevent similar incidents in the future.
Security precautions were increased after the blast, with authorities evacuating all schools and kindergartens in North Ossetia.
Six years ago, Islamist separatists carried out one of the worst attacks in Beslan, North Ossetia, in which more than 330 people were killed - including 168 children.
The neighbouring republics of Dagestan and Chechnya have seen repeated attacks by the separatists.
Medvedev ordered his special envoy for the northern Caucasus, Alexander Kloponin, to travel to Vladikavkaz. Police in the city defused a second bomb at the entrance to the marketplace, after the first one went off.
Putin accused the terrorists behind the car bombing of seeking to sow discord.
"We are counting on the Muslim population to make a decisive contribution towards the fight( against terrorism), Putin said.
Islamic separatists in the Muslim north Caucasus are fighting elements loyal to the Kremlin with the goal of setting up an independent "Caucasus Emirate" in the region.