Eleven people were killed by a suspected terrorist blast that ripped through a minibus in the southern Russian city of Vladikavkaz on Thursday, security forces were quoted as saying by Russian news agencies.

The blast occurred in a busy street in the centre of the city, which lies in the North Ossetia region of the restive Russian Caucasus.

Witnesses said the bus was packed with people at the time of the blast.

"As passengers were getting on and off an explosion occurred outside the vehicle," Interfax quoted an anonymous press officer for the local branch of the interior ministry as saying.

The investigative committee of the Russian prosecution service put the latest death toll at 11 and said it had opened a terrorism investigation, Interfax and RIA Novosti news agencies reported.

Interfax quoted emergency services as saying 28 injured people had sought medical help.

In the immediate aftermath, bodies could be seen lying in the road around the badly damaged white public minibus.

Large crowds gathered around a police cordon to view the damage, television pictures showed.

North Ossetia lies on Russia's southern border with Georgia.

The region was the scene of the devastating 2004 school hostage crisis at Beslan and lies close to several regions racked by instability in recent years, including Chechnya, Dagestan and Ingushetia.