MOSCOW: A female suicide bomber killed 14 people Sunday when she blew herself up at the main train station in the southern city of Volgograd, raising concerns about security in Russia just six weeks before the Sochi Olympic Games.

The unidentified woman set off her charge after being stopped by a police officer at the metal detectors at the entrance to the station while it was packed with people travelling to celebrate the New Year, regional officials said.

Footage of the blast captured by a nearby camera showed a huge fireball blow out the front doors and a row of windows from the grey stone three-story building, before huge billows of smoke poured out as people scattered along the street.

Russia's Investigative Committee spokesman Vladimir Markin said officials had launched an inquiry into a suspected “act of terror”.

“A suicide bomber who was approaching a metal detector saw a law enforcement official and, after growing nervous, set off an explosive device,”Markin said in televised comments.

Officials said at least 34 people were injured by the blast that had the explosive equivalent of more than 10 kilogrammes (16 pounds) of TNT. It was the deadliest attack in Russia for almost three years.

The police officer who spotted the woman died in the attack while several others who were stationed at the metal detectors were wounded by the blast.

State television said their actions prevented “hundreds” from being killed.

The lifenews.ru website meanwhile posted a picture of what it said was the head of the young female bomber lying amid a pile of debris with her long brown hair spread across the floor.

“It was a very powerful blast,” train station store attendant Valentina Petrichenko told the Vesti 24 news channel.

“Some people started running and others were thrown back by the wave of the blast,” she said.

“It was very scary.” Volgograd Mayor Irina Guseva vowed on Vesti 24 television: “We will not allow panic to grip this city.”

Olympic security fears

The city of Volgograd, known as Stalingrad in the Soviet era, was already attacked in October by a female suicide bomber with links to Islamists fighting federal forces in the nearby volatile North Caucasus.

The October 21 strike killed six people aboard a crowded bus and immediately raised security fears ahead of the February 7-23 Winter Games in Sochi.

The Black Sea city lies 690 kilometres (425 miles) southwest of Volgograd and in direct proximity to the violence ravaging daily in North Caucasus regions such as Dagestan and Chechnya.

Militants are seeking to impose an Islamist state throughout Russia's North Caucasus. Their leader Doku Umarov has ordered rebels to target civilians outside the region and disrupt the Olympic Games.

President Vladimir Putin staked his personal reputation on the Games' success by lobbying for Sochi's candidacy before the International Olympic Committee and then spending more than $50 billion (36 billion euros) for the event.

The Kremlin said Putin was “immediately” informed of the attack.

“The president is receiving reports as the events develop and as new information comes in, first of all, this concerns the number of people injured and killed,” Putin spokesman Dmitry Peskov told Russian state television.

Militant attacks have become part of daily life in the mainly Muslim Northern Caucasus but the Volgograd blast will be a particular concern to the authorities as the bomber struck a city of over one million in the Russian heartland.

The Volgograd attack is deadliest in Russia since the suicide bombing on Moscow's Domodedovo airport in January 2011 that killed 37.

'Security stepped up'

Russia's interior ministry said separately that it was immediately stepping up security at all the nation's main train stations and airports.

“These measures involve a greater police presence and more detailed passenger checks,” an interior ministry spokesman told the Interfax news agency.

Russian authorities have repeatedly vowed to take the highest security precautions in Sochi. There have been few indications to date of foreign sports fans cancelling their attendance out of security fears.

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.

Female suicide bombers set off blasts at two Moscow metro stations in March 2010 that killed more than 35 people.

So-called black widows were also responsible for killing more than 90 people when they took down two passenger jets that took off from a Moscow airport within minutes of each other in 2004.