Russian police have detained three men suspected of involvement in Thursday's bomb attack in the city of Vladikavkaz, in Russia's Caucasus region.
A suicide bomber struck a crowded open-air market in the capital of North Ossetia, killing himself and at least 16 people and wounding some 120 others.
Russian investigators say the attacker detonated a 30-kilogram bomb packed with bolts and metal fragments just outside the main entrance to the market shortly before noon local time.
There was no immediate claim of responsibility.
Prime Minister Vladimir Putin said crimes like the bombing are committed to stir ethnic discord and must be stopped.
The majority of people in North Ossetia are Orthodox Christians, unlike nearby Chechnya, Ingushetia and Dagestan, which are predominantly Muslim.
North Ossetia has seen several attacks blamed on Islamist militants. The worst came in September of 2004 when gunmen seized a school in Beslan, taking more than 1,000 hostages. Russian troops stormed the school a few days later and about 330 people, half of them children, were killed.
A 1999 bomb attack in Vladikavkaz killed more than 50 people and another one in 2001 killed six people. Attacks on government targets are also frequent in neighboring Muslim-populated regions of Dagestan, Chechnya and Ingushetia.
U.S. President Barack Obama expressed condolences to the victims and said the bombing underscores the resolve of the United States and Russia to join forces in fighting terrorism.
Some information for this report was provided by Reuters.