RUSSIA ON HIGH ALERT

The IOC has said it is confident that the Games, opening in Sochi on the shores of the Black Sea on February 7, will be safe, and Putin has put about 37,000 security personnel on combat alert in the Black Sea resort and increased security nationwide.

Russia has also been discussing its security operation with the United States, and Putin, who has played a big role in winning and organising the Games, spoke about security at Sochi with U.S. President Barack Obama by telephone on Tuesday.

Even so, Moscow has failed to dampen concern that it will be able to guarantee visitors' and competitors' safety, despite the most elaborate security preparations for an Olympics.

A militant leader, Doku Umarov, has called for insurgents fighting for an Islamist state in Russia's North Caucasus to attack Sochi - which lies on the western edge of the Caucasus mountains where the insurgency is focused.

Security concerns were heightened by the suicide bombings last month in Volgograd, a southern Russian city which serves as a gateway to the North Caucasus, and by a video in which the Islamist militant group which claimed responsibility for the attacks threatened more violence.

In Sochi, which plans to host hundreds of thousands of visitors during the Games, security forces are searching for a woman called Ruzanna Ibragimova, 23, who they suspect may be planning a suicide attack.

She may have arrived in the Olympic host city on January 11-12, a letter seen by Reuters said.

"(She) may be used as a terrorist-suicide bomber by (insurgency) leaders to organise terrorist acts during preparations for and during the 2014 Winter Olympics," read the letter, asking police to look immediately into the matter.

The letter from Russia's Federal Security Services to local police said she was the widow of a slain Islamist militant and is believed to have recently left her home in Dagestan, in the turbulent, mainly Muslim North Caucasus.

Photographs of Ibragimova show a woman in a hijab, wearing a long dress.

Some Russian media say Russian forces may also be looking for other would-be suicide bombers known as "Black Widows", but the reports have not been confirmed.

Obama, Putin discuss Olympics security in call	Russia imposes security clampdown in Sochi before Olympics