The International Olympic Committee president says he has confidence that Russian authorities will deliver a "safe and secure" Games in Sochi.
Thomas Bach wrote to President Vladimir Putin to express condolences for the two deadly attacks that struck Volgograd within 24 hours.
Investigators say the attacks on a railway station and trolleybus, which killed at least 31 people, were linked.
They struck just over a month before the Winter Olympics begin in Sochi.
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