The Transportation Security Administration has temporarily barred passengers on direct U.S. flights to Russia from packing any liquids in carry-on bags.
The anti-terrorism measure banning carry-on liquids, powders, aerosols and gels was announced by Delta Air Lines -- the only U.S. airline with regular nonstop travel to Russia -- on Thursday, the New York Times reported.
The new security rule closely follows reports that the Homeland Security Department had warned airlines flying to Russia to be on alert for toothpaste tubes filled with explosive ingredients that terrorists might use to blow up an aircraft or smuggle into Sochi for attacks during the Winter Olympics.
The measure will be in force for the next month. Passengers are still permitted to bring liquids in their checked luggage, Time reported.
U.S. and European security officials think terrorist strikes are likely to occur during this month's Olympics, which end on Feb. 23, though the risk appears to be higher in areas of Russia other than Sochi, Reuters reported. Unidentified officials said there continue to be breaking intelligence reports about potential Olympics-associated terrorism threats.
"I'm more concerned now than a week ago," a U.S. official said on Thursday. A number of extremist organizations have hinted at plans to conduct strikes during the Olympics, he said.
The official said that although Sochi sports installations are well protected, nearby there are other more vulnerable public areas where extremists could be able to mount strikes.
"We think the ... greater danger from a terrorist perspective is in potential for attacks to occur outside of the actual venues of the games themselves in the area surrounding Sochi or outside of Sochi in the region," said Matthew Olsen, head of the National Counterterrorism Center, at a U.S. House hearing earlier this week.
The biggest danger, according to U.S. and European officials, comes from the Caucasus Emirate.
Some Russian officials think foreign news organizations are overdramatizing the terrorist threat to the Winter Games, the Christian Science Monitor reported.
"The level of fear should be lower," Russian Deputy Prime Minister Dmitry Kozak said. "The level of threat in Sochi is no worse than in New York, Washington, or Boston" -- cities that all have come under highly publicized terrorist attacks.