MOSCOW (Reuters) - A big explosion rocked a market on Friday in the city of Vladikavkaz in Russia‘s volatile North Caucasus region, causing an unspecified number of casualties, Russian news agencies said. Itar-Tass news agency said the blast was caused by an explosive device, but other news agencies made no mention of bombs. Russia‘s Interior Ministry was unable to confirm the explosion in Vladikavkaz, which is the capital of the North Ossetia region and is 50 km (31 miles) from breakaway Chechnya. An Emergencies Ministry official confirmed by telephone from Vladikavkaz that there had been an explosion but gave no details. The Russian news agencies said the blast tore through the market at about 11.20 Moscow time (0820 GMT). "There are casualties," Tass said, adding that an explosive device had been placed in a shop. It did not give a source for the information. Chechnya‘s nearly two-year war of independence with Moscow ended in 1996 but the North Caucasus remains votatile.