At least 13 people are reported killed in the explosion at a railway station in the southern city of Volgograd.
A female suicide bomber has been blamed for an
explosion at a railway station in Russia which is thought to have left
at least 13 people dead.
The blast, at a station in the southern city of Volgograd, is thought to have left another 40 people wounded.A National Anti-Terror Committee official was quoted as saying that a female suicide bomber was responsible.
She apparently detonated a bomb in front of a metal detector inside the main entrance of the station.
Russian President Vladimir Putin ordered law enforcement agencies to take "all necessary measures".
Federal police spokesman Vladimir Kolesnikov said security would be stepped up at train stations and airports.
Regional interior ministry spokeswoman Svetlana Smolyaninova told the ITAR-TASS news agency that the explosion took place inside the train station at around 12.45pm local time (8.45am UK time).
One witness, who gave his name as Vladimir, told a Russian TV station: "I heard the blast and ran toward it.
"I saw melted, twisted bits of metal, broken glass and bodies lying on the street."
Train station store attendant Valentina Petrichenko said: "It was a very powerful blast.
"Some people started running and others were thrown back by the wave of the blast. It was very scary."
The attack comes just weeks before the start of the Winter Olympics in Sochi, a town 430 miles southwest of Volgograd.
Sky News Moscow producer Yulia Bragina said: "It's very concerning with two months to go to the Sochi Olympics.
"The Russian security services are working 24/7 to make the Games safe for the sportsmen and people who want to visit the Olympics in Russia.
"There will be a big investigation into what has happened."
A female suicide bomber killed seven people in Volgograd in October, one of the deadliest such attacks outside the troubled North Caucasus region in more than two years.
Known as Stalingrad in Soviet times and previously as Tsaritsyn, Volgograd is an important industrial centre with a population of over a million.
On Friday, a car bomb killed three people in the southern city of Pyatigorsk, 170 miles east of Sochi.
In July, Doku Umarov, one of the leaders of an ongoing insurgency in the North Caucasus, an area close to Sochi, urged militants to use "maximum force" to disrupt the Winter Olympics, a project close to Mr Putin's heart.
Organisers have pledged to make Sochi the "safest Olympics in history".
Female suicide bombers in Russia are often known as "black widows" who aim to avenge the deaths of their militant husbands.
So-called "black widows" were responsible for explosions at two Moscow metro stations in March 2010 which left more than 35 people dead.
