The blast has left another 50 injured - 27 of them seriously, and highlights security concerns for the Games, which are set to take place 400 miles away on February 7 until 23, with the Paralympics following on March 7until 16.

A police officer is reported to be among the dead, while a nine-year-old girl is among the injured.

"According to verified information, the explosion at the railway station in Volgograd has claimed 16 lives," Russia's Investigative Committee said.

Video footage captured at the moment of the blast shows a massive orange fireball filling the hall of the station, which was busier than usual with people travelling home for the New Year holiday, as clouds of grey smoke poured out of the shattered windows.

President Vladimir Putin has ordered that "all necessary security measures" be taken to assist survivors and provide security in Volgograd, while the United Nations Security Council has condemned the bombing "in the strongest terms" and sent its condolences to the victims and their families.

Russia's President Vladimir Putin has ordered that all necessary security measures be taken to assist the bomb survivors and provide security in Volgograd ©AFP/Getty Images

Meanwhile, a Federal Police spokesman said security would be stepped up at train stations and airports.

Although no group has yet claimed responsibility for the shrapnel-filled bomb, early reports suggest that the attack was carried out by a female suicide bomber, who blew herself up after a police officer started to approach her near the metal detector at the entrance to the station as she looked suspicious.

Authorities were said to have identified her as Oksana Aslanova, a resident of Dagestan, the province adjacent to Chechnya and now the centre of a long-running Islamist insurgency, and widow of a leader of a militant group, however the Interfax news agency then cited two unidentified law enforcement sources as saying the attacker was believed to be a man who carried a bomb into the station with a rucksack.

Other reports suggest the attacker may have been accompanied by a man with a rucksack and another woman.

Today's terrorist attack is the second in Volgograd in recent months - with the first killing six on a bus in October, while a car bomb killed three people in the southern city of Pyatigorsk on Friday (December 27).

The International Olympic Committee (IOC) has maintained that it is confident that enough is being done to ensure the safety of visitors to the Sochi 2014 Games.

"Our condolences go to all those affected by today's bombing in Volgograd," a spokesman told insidethegames.

"Unfortunately, terrorism is a global phenomenon and no region is exempt, which is why security at the Games is a top priority for the IOC.

"At the Olympics, security is the responsibility of the local authorities, and we have no doubt that the Russian authorities will be up to the task."

The IOC has said that security at the Sochi 2014 Olympic and Paralympic Games is a "top priority" ©AFP/Getty Images

Declassified Canadian intelligence reports earlier this month reiterated the dangers of terrorism at Sochi 2014 and, in particular, the threat posed by Islamist group Imarat Kavkaz and its Chechen leader Doku Umarov, who urged followers to use "maximum force" to prevent the staging of the Games in a video posted online in July this year.

Russia pledged to join forces with both the United States and the United Kingdom earlier this year to help boost security at major sport events, including the Olympic and Paralympic Games.

"Security is the number one priority for every Olympic Games and Sochi 2014 is no different," a Sochi 2014 spokesman told insidethegames.

"The authorities are managing security in a highly rigorous way and we are confident the Games in Sochi are going to be safe and comfortable for all."

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