At least 25 people have died and over 100 have been injured after a luxury 14-car passenger train carrying 661 people derailed in Russia, following a bomb attack.

The Nevsky Express, from Moscow-Saint Petersburg, was on its way nearly 280km from its destination when four carriages jumped the tracks near the town of Bologoye on the border between the Tver and Novgorod regions.

The derailment has been caused by a bomb equivalent to 7kg of TNT and is suspected to be a terrorist attack, according to officials.

A criminal investigation into the matter has begun and Russian Railways staff are now carrying out repair work on the line.