The US Homeland Security Department is warning airlines flying to Russia that terrorists may try to smuggle explosives on board hidden in toothpaste tubes.
The threat is to airlines that have direct flights to Russia, including some that originate in the United States, said a law enforcement official speaking on condition of anonymity because he was not authorised to discuss details of the warning.
Russian forces are on high alert to head off possible militant attacks at the Winter Olympic Games, which begin on Friday in Sochi. Some US lawmakers have expressed concern about security at the Black Sea resort, but US President Barack Obama has said he believed Sochi was safe.
Suicide bombers killed 34 people in the Russian city of Volgograd, 700km northeast of Sochi, in December. The attacks raised fears of violence at the Olympics.
The department said in a statement that the US "isn't aware of a specific threat to the homeland at this time".
The statement notes the department - quote - "regularly shares information with domestic and international partners, including those associated with international events such as the Sochi Olympics".
In 2009 a Nigerian man tried to set off an explosive hidden in his underwear aboard a US-bound airliner. In 2001 a man tried to blow up a jumbo jet with explosives in his shoes.
- AP, Reuters