Russia 'black widow' suicide bombing sparks terror fears at Sochi Olympics

New wave of terrorism fears looms over Winter Olympics in Sochi after a suicide bombing at a railroad station in central Russia killed 15 people on Sunday.

The explosion struck the main railroad station in Volgograd, a city about 885 km south of Moscow at 12.45pm.

The bomb, which officials said was kept in a bag pack, blew out windows in the building's facade and left a horrific scene of carnage at the station's main entrance.

According to the Sydney Morning Herald, the blast, captured on a surveillance video camera from across the central plaza in front of the station, occurred near the metal detectors.

Vladimir I. Markin, a spokesman for the Investigative Committee, called the bombing an act of terrorism.

The exact motivation, target and perpetrator were not immediately clear.

Within hours of the attack, the authorities blamed a suicide bomber, citing the gruesome discovery of a woman's severed head, which could aid in identifying her, the report said.

Female suicide bombers are often referred to in Russia as 'black widows' - women who seek to avenge the deaths of their family members in North Caucasus fighting by targeting Russian civilians, it added.