With the death toll from Sunday and Monday's suicide bombings officially at 34, Russian authorities have increased security in the city of Volgograd, where the attacks took place, and across the country amid concerns about terrorism at the upcoming Winter Olympics in Sochi.

As part of Operation Anti-Terror Whirlwind, more than 5,000 police and troops were deployed in Volgograd on Monday. "I think we will be able to solve these crimes, particularly because we have some clues," Federal Security Service director Aleksandr V. Bortnikov said, according to the New York Times.

Police are reportedly targeting migrant workers from the Caucasus and from former Soviet states. At least 87 people were detained on Monday and early Tuesday after they resisted questioning or failed to produce identification, though there was reportedly no evidence linking them to the bombings.

Despite the two bombings, and another suicide blast last month, Russian authorities and Olympic committee members have expressed confidence, publicly at least, that the games in Sochi will be safe.

"I am certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games," Thomas Bach, the president of the International Olympic Committee, said in a statement on Monday.

[Image via AP]