Two weeks before the Winter Olympics, Russian security forces are reportedly searching for potential suicide bombers, at least one of whom may already be in the host city of Sochi.
The suspects are thought to be linked to Islamist militants who are fighting to throw off Russian control and create a fundamentalist Muslim state in Russia's North Caucasus Mountains.
Police have been circulating leaflets at hotels in Sochi, warning about women who may be part of a terrorist plot.
They are known as "black widows," sent to carry out suicide bombings in revenge for husbands or family members ki