Updated at 10:00 a.m. Eastern
MOSCOW Russian investigators say a female suicide bomber has struck a passenger bus in the southern city of Volgograd, killing five people and injuring at least 20 others.
The state ITAR-Tass news agency cited Valery Safonov, an official with Russia's main investigative agency, saying the suspected bomber was the partner of a militant.
The suspected bomber was from Dagestan, one of the predominantly Muslim republics in the North Caucasus, said Vladimir Markin, the spokesman for the Investigative Committee, Russia's main investigative agency. In a statement, he identified the woman as 30-year-old Naida Akhiyalova.
No one immediately claimed responsibility.
Monday's explosion was the first on a bus in Russia since a 2008 bombing carried out by a female suicide bomber in the North Caucasus, a region in southern Russia where an Islamic insurgency is simmering.Volgograd is located about 400 miles to the northeast of the North Caucasus, but Monday's bombing was certain to add to security fears ahead of the Winter Olympics in Sochi in February. Sochi sits to the west of the North Caucasus, along the Black Sea.
Markin said at least five people died and 32 were hospitalized, including eight who were in serious condition. It was unclear whether the suicide bomber was listed among the dead.
The explosion occurred at a bus stop near a timber storage site. The bus remained in one piece but the windows were blown out.
A total of 40 people were on the city bus at the time of the explosion, said Irina Gogolyeva, a spokeswoman for the Emergency Situations Ministry.