MOSCOW - Four people were killed and 10 injured Sunday when a blast tore through a train station in the southern Russian city Volgograd ahead of February's Winter Olympic Games in nearby Sochi.
Regional interior ministry spokeswoman Svetlana Smolyaninova told the ITAR-TASS news agency that the blast occurred inside the train station at around 12:45 pm (0845 GMT).
"According to the latest information, which is preliminary, four people died as a result of the blast," Interfax quoted an unnamed local emergencies ministry official as saying.
"Ten people were injured, but their number could grow," the emergencies ministry official said.
ITAR-TASS said the blast occurred near the metal detectors stationed at the entrance to the city's main train station.
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 Russia's volatile North Caucasus.
The October 21 strike killed six people aboard a crowded bus and immediately raised security fears ahead of the February 4-23 Winter Games in Sochi.
The Black Sea city lies 690 kilometres (425 miles) southwest of Volgograd and in direct proximity of 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.
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 taking down two passenger jets that took off from a Moscow airport within minutes of each other in 2004, killing about 90 people.