At least 15 people died and 87 were injured in an explosion in Russia's North Caucasus city of Vladikavkaz, investigators said.

The blast occurred near the city's central market at 11:22 Moscow time (07:22 GMT).

The explosive device, equivalent to 30-40 kg of TNT, was detonated by a suicide bomber in a Volga car, spokeswoman Maria Gatsoyeva said.

A local police source said the bomber had been identified as a man named Archiyev and the car owner's name was Dobriyev.

The market has been the target of two earlier terrorist attacks.

In 1999, an explosion killed 55 people and injured 300 others. In 2008, 12 people were killed and over 40 injured in a bus bombing.

President Dmitry Medvedev called on officials to help the injured and start investigations into the incident.

Medvedev's envoy to the North Caucasus, Alexander Khloponin, is on his way to Vladikavkaz on the president's orders.

Vladikavkaz is the capital of the republic of North Ossetia, one of the many terrorism hotspots in Russia's troubled North Caucasus region.

North Ossetia, as well as neighboring Dagestan and Chechnya, have seen increasing violence in recent years, with shootings and bomb attacks becoming regular occurences. Officials have vowed to clamp down on militant groups.

MOSCOW, September 9 (RIA Novosti)