Two suicide bombings within 24 hours killed at least 31 people in a southern Russia city, highlighting the terror threat Russia faces as it prepares to host the Winter Games in six weeks.
A suicide bomber on a bus early Monday in Volgograd killed at least 14 people and left nearly 30 wounded, Russian officials said, a day after another suicide bombing killed at least 17 at a railway station in the city.
Vladimir Markin, the spokesman for Russia's main investigative agency said Monday's blast involved a bomb similar to the one used in Sunday's bombing at the city's train station.
"That confirms the investigators' version that the two terror attacks were linked," Markin said in a statement. "They could have been prepared in one place."
No one immediately claimed responsibility for the attacks, but they came several months after Chechen rebel leader Doku Umarov called for attacks against civilian targets in Russia. Umarov, leader of a terrorist group that calls itself the Caucasus Emirate, has called on Muslims to disrupt the Olympics, which will be held in Sochi.
"If you are a terrorist group in the Caucasus, the Sochi Olympics are going to be a very inviting target," says Steven Pifer of the Brookings Institution's Arms Control and Non-Proliferation Initiative.
Some Muslim terrorists view the Olympics as a provocation, says Jeffrey Mankoff of the Center for Strategic and International Studies' Russia and Eurasia Program. Sochi was conquered in the 19th century. "They view it as a provocation on territory they consider stolen from Muslims," he says.
The government has deployed tens of thousands of soldiers, police and other security personnel for the Games, and it has introduced some of the most extensive identity checks and security measures seen at an international sports event.