Cossacks, snipers and spooks shipped in to support the feared FSB agents in securing Sochi

PRESIDENT Vladimir Putin's most trusted weapon in Sochi is the covert surveillance offered by the feared FSB.

RUSSIA'S heavily armed men in black are part of the biggest special forces brigade ever assembled to guard the Sochi Olympic's Opening Ceremony from Islamic terrorists hellbent on bloody revenge.

These special rapid response officers join 70,000 highly trained protection forces shipped into Sochi, including Federal Security Service (FSB) spies, Russian Army snipers, fiercely nationalistic Cossacks and police from the Department of Internal Affairs.

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News_Rich_Media: Security concerns continue to grow ahead of the Sochi Games, with teams ramping up safety measures amid fears of kidnapping after two Australian athletes received threats that are being investigated by counter-terrorism experts.

Sochi's battle to neutralise Muslim jihadists from the nearby Dagestan province, regarded as the danger capital of Europe, extends to cloud-shaped drones in the sky, submarines in the Black Sea and car bomb squads.

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But counter-terrorism experts who have war-gamed Russia's defences told News Limited that President Vladimir Putin's most trusted weapon is the covert surveillance offered by the feared FSB, the successor agency of the KGB.

News_Image_File: Russian Cossacks patrol a platform at the Olympic Park train station ahead of the Sochi Games.

"They will use a variety of covers, including cleaners, foreign-looking spectators, snow plough drivers and agents dressed in athlete uniforms or acting as homeless people," said security specialist Andrew McWhinney of Sydney's Intelligent Risks, which was hired by Olympic chiefs to analyse Sochi's security.

"The FSB are renowned for using disguises, including wigs, beards and make-up - possibly using several thousand agents, the best they have."

News_Image_File: Workmen or spooks in the athletes' village?

In the days leading up to the Opening Ceremony, News Limited tried to photographed what appeared to be cleaners and maintenance workers in one of the Olympic athletes' villages but it provoked an angry response.

Tens of thousands of police manning metal detectors in Olympic venues are also blending into their surroundings by wearing casual uniforms similar in design to official Sochi 2014 volunteers.

The army of spooks, snipers and special forces faces its first test when athletes march into the $779 million Fisht Olympic Stadium for the first Olympics on Russian soil since the boycotted 1980 Moscow Games.

Former British Royal Marine commando officer Scott Howe - who has operated in Iraq, Libya and ex-Soviet states such as Latvia and Lithuania - said Dagestan, which lies 500km east of Sochi in Russia's North Caucasus, is the most dangerous place in Europe.

Doku Umarov, a widely known Chechen rebel leader, urged Islamic militants in the region to "do their utmost to derail" the Games, which he described as "satanic dances on the bones of our ancestors."

A chilling video released last month by two purported suicide bombers warned Olympic tourists to expect a "surprise package".

News_Rich_Media: Terrorism experts believe Sochi is secure, but warn that every threat to the Winter Olympics must be taken seriously.

"If it happens [the Olympics], we'll have a surprise for you," they said. "This is for all the Muslim blood that is shed every day around the world, be it in Afghanistan, Somalia, Syria ... This will be our revenge."

Australia's Olympians have been ordered to stay within Sochi's security "bubbles" and only travel between them on designated Olympic transport. They will leave Russia as soon as the Games are over.

News_Image_File: Sochi volunteers and security personnel man a check point in the Black Sea resort town.

Olympic tourists, including athletes' families, have been warned not to travel by rail between Moscow and Sochi, to only book accommodation through official channels, and to stay away from "places of mass assembly" outside the Games venues.

News_Image_File: tennis tennis

News_Image_File: What's going on? A schedule of the games. News_Image_File: A history of the Winter Olympics.