A blast tore into a public minibus packed with students in a busy city square in Russia's Caucasus region Thursday, killing at least nine, investigators said.

At least 40 people were wounded in the blast, blamed on terrorism, that occurred close to the busy central market in Vladikavkaz, the capital of North Ossetia, the regional administration said.

Many of the injured suffered severe burns, officials said. Body parts were found at the scene.

North Ossetia is a Russian region that borders South Ossetia, the separatist enclave where Russia and Georgia had a short, bloody confrontation last August,

"As a result of the terrorist act in Vladikavkaz, nine people died and around 40 were injured," regional administration President Taimuraz Mamsurov was quoted by the Russian non-governmental news agency Interfax as saying.

The blast, apparently at a bus stop and not inside the minibus, was likely "caused by a female terrorist suicide bomber," Mamsurov said.

Russian President Dmitry Medvedev ordered investigators to carry out a "painstaking" criminal inquiry into whether the bombing was a terrorist attack, RIA Novosti reported.

A day of mourning will be observed in the region Saturday, Mamsurov said.