A female suicide bomber blew herself up in the entrance hall of a train station in southern Russia, killing at least 16 people as the country prepares to host the Winter Olympics in nearby Sochi.
Volgograd officials said the woman set off her charge after being stopped at the metal detectors at the entrance to the city's main train station while it was packed with afternoon travellers.
Video: Female suicide bomber hits Russia train station
"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."
State television footage showed windows blown out across the top two floors of the grey brick building and numerous ambulances gathered at the station's front entrance amid piles of debris and snow.
"Initial indications are that the blast was set off by a female suicide bomber," the National Anti-Terror Committee said.
President Vladimir Putin ordered law enforcement agencies to take all necessary measures to ensure security, RIA news agency quoted his spokesman as saying. A federal police spokesman, Vladimir Kolesnikov, said security would be stepped up at train stations and airports.
Doctors and police said 15 people plus the bomber were killed and nearly 45 injured.
The lifenews.ru website published 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.
The website identified the bomber as a woman named Oksana Aslanova who had been married to two different Islamists killed in battles with federal forces in the North Caucasus.
The city of Volgograd - known as Stalingrad in the Soviet era - was attacked in October by a female suicide bomber with links to Islamists fighting federal forces in the nearby volatile North Caucasus region.
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 southwest of Volgograd and in direct proximity to the violence ravaging North Caucasus regions such as Dagestan and Chechnya on a daily basis.
Militants are seeking to impose an Islamist state throughout Russia's North Caucasus. Their leader Doku Umarov has ordered his foot soldiers to target civilians outside the region and disrupt the Olympic Games.
Putin staked his personal reputation on the Games' success by lobbying for Sochi's candidacy and then spending more than US$50 billion on the event.
Agence France-Presse, Reuters, Associated Press