US bans carry-on liquids on Russia flights

US authorities have announced a temporary ban preventing travellers from bringing any liquids, gels or aerosols aboard Russia-bound flights amid a security threat to the Winter Games.

The US Transportation Security Administration directive came a day after Washington warned American and foreign airlines that extremists may target them by placing explosives in toothpaste or cosmetic tubes in an attempt to disrupt the Olympics, set to start on Friday in Sochi.

The banned items, however, can be placed in customers' checked baggage, and prescription medications are allowed.

President Barack Obama, meanwhile, said Russia had an "enormous stake" in thwarting terrorism at the Games, adding that Washington was doing everything it could to help keep athletes safe.

"I think the Russians have an enormous stake, obviously, in preventing any kind of terrorist act or violence at these venues. They have put a lot of resources into it," Obama said in an interview with US Olympic television host NBC.

Russia last month banned domestic travellers from having any liquids and gels, including toothpaste, in their carry-ons.

Stringent rules about liquids and toothpaste in hand luggage have been standard practice on US carriers after a string of thwarted bomb plots in the years following the September 11, 2001, attacks.

But, until now, limited amounts were allowed on board.

Delta Airlines said on its website that customers travelling between the two countries would have to check in with an airline representative at the airport, not online or using their smartphone or airport kiosks.

The chairman of the US House Homeland Security Committee said Americans were not specifically targeted by the toothpaste explosive threat.

"The beef they have is really with the Russians," Representative Mike McCaul told CNN.

"However, if you blow up an aeroplane, you will have innocent civilians that could include Americans."

He said the plot originated from the leader of the Chechen rebel extremists, Doku Umarov, who called for attacks on the Games in a video released in July.

The Texas Republican also hailed Russian officials for co-operating with the United States on the threat, despite simmering tensions between the former Cold War foes.

Concerns over security at the Games, which run until February 23, skyrocketed after two suicide attacks that killed 34 in the southern Russian city of Volgograd in December, blamed on extremist militants from the Northern Caucasus region.

Russian security forces are still fighting insurgents in the area, which is close to Sochi, and militants have threatened to strike targets in Russia during the Olympics.

About 40,000 members of the Russian security forces are on duty in and around Sochi in one of the tightest operations ever mounted at an Olympics.

Two US warships have arrived in the Black Sea and will stand ready to offer assistance in the case of a security emergency, including the evacuation of Americans in the event of an attack.