International Olympic Committee (IOC) President Thomas Bach attends a news conference at the IOC headquarters in Lausanne December 10, 2013. [Photo/Agencies]

Still, the Volgograd bombings have brought home the security threat to Olympic athletes and administrators preparing to travel to Sochi.

Rene Fasel, president of the international ice hockey federation and head of the umbrella group of winter Olympic sports bodies, said security in Sochi will be similar to Salt Lake City when it hosted the 2002 Winter Games just months after the September 11, 2001, terror attacks in the U.S.

"It will be very difficult for everybody. People will complain about security," Fasel said in an interview with The Associated Press. "I'm sure the Russians will do everything possible, but that means we will have an unbelievable (tight) security control."

Fasel said the Olympics should not bow to the terror threats.

"We have to be strong," he said. "We decided to go to Sochi and the only answer to these bombings and terrorist incidents is to go there."

Norwegian cross-country skier Marit Bjoergen said Sunday she was frightened by the first attack in Volgograd.

"It's still difficult to say whether it has anything to do with the Sochi Olympics," she told Norwegian broadcaster NRK. "This came suddenly and I need to find out more about it. But one is slightly prepared for this kind of thing to happen and of course I'm a bit scared. I'm counting on that they will take good care of us and that we have good security during the games in Sochi."

Gerhard Heiberg, a Norwegian IOC member who organized the 1994 Winter Games in Lillehammer, said he was not surprised that bombings have occurred ahead of the Sochi Games but voiced confidence in the Russian security plans.

"I feel that everything that is humanly possible is being done," he told the AP. "When we come to Sochi, it will be impossible for the terrorists to do anything. The village will be sealed off from the outside world."

The British Olympic Association said it was monitoring the situation in Volgograd and was in regular contact with the Foreign Office, police, the IOC, other governing bodies and athletes.

"Our preparations for the Sochi 2014 Olympic Winter Games continue and we are confident the Russian officials will regularly assess the security measures that are in place to make certain the environment is as safe as possible," the BOA said.