Five people have been killed after a passenger bus exploded in Russia’s Republic of North Ossetia. At least thirteen were injured. An explosive device has been found in the back of the mangled bus, and authorities are not ruling out a terrorist attack.

It was a routine trip for most of the 18 passengers aboard the bus, but it ended in tragedy. A powerful explosion set the bus on fire as it stopped for a routine check at a police checkpoint. Four people, including one child were killed at the scene. One other died an hour later in hospital.

Those injured were immediately rushed to a nearby hospital, where they are being treated both for physical wounds and severe stress.

The site of the tragedy

The bus, which was less than half full, was travelling from Pyatigorsk in the Stavropol region to Vladikavkaz in North Ossetia.

Police aren't ruling out a terrorist attack.

While police are collecting evidence at the scene, it's still unclear exaxtly what happened. Sources close to the investigation say that two men got off the bus a few minutes before it arrived at the checkpoint and they might have left an explosive device.

Previous terrorist attacks in the region

In September 2004, armed terrorists attacked School 1 in the nearby Ossetian town of Beslan.

The attack resulted in the deaths of 334 people, most of them children, as the school building collapsed and burned to the ground after several explosions.

Just over a year later, in October 2005, more than 200 armed terrorists attempted to take control of several government buildings in the Kabardino-Balkar capital of Nalchik.