Authorities in southern Russia say a female suicide bomber set off a blast at a train station in the southern city of Volgograd, near the volatile North Caucasus region, killing at least 14 people and wounding several dozen others.
Russia's Investigative Committee spokesman Vladimir Markin says the bomber detonated her explosives in front of the metal detectors at the entrance of the city's main station early Sunday morning.
Officials says more than 40 people were wounded by the bomb which contained more than 10 kilograms of TNT.
No one has claimed responsibility for the attack. However, the Interfax news agency reports that the suspected bomber's head was found at the site of explosion, allowing authorities to quickly identify her.
Russian President Vladimir Putin has ordered the country's law enforcement bodies to tighten security.
The attack comes weeks before the Winter Olympics in the Black Sea city of Sochi, about 650 kilometers south of Volgograd. There have been Islamist militant threats against the Winter Games.
An attack in Volgograd by a female suicide bomber on October 21 killed five people and wounded around 30. Russia's Investigative Committee identified that suicide bomber as a 30-year-old resident of Dagestan, one of the republics in Russia's predominantly Muslim North Caucasus region.
In recent years, Dagestan has become the epicenter of an ongoing Islamist insurgency in the North Caucasus.
In early July, the leader of the Islamist insurgency in the North Caucasus, Doku Umarov, declared an end to a moratorium on attacks on Russian civilian targets he had announced the previous year.
He also called on insurgents to target the 2014 Winter Olympics set to begin in February in Sochi.