Italian authorities will close the airspace over Turin on Friday when athletes and foreign dignitaries, including US first lady Laura Bush, attend the Winter Olympics [Images] opening ceremony.

The no-fly order was the latest move to protect the thousands of athletes and at least 15 visiting foreign leaders gathering in Turin for the Games, which start with the opening ceremony at 8 p.m. (1900 GMT) on Friday.

No flights will be permitted in or out of Turin's Caselle airport from 6:45 p.m. (1745 GMT) to 11:15 p.m. (2215 GMT) on Friday, airport operator Sagat said in a statement.

Exceptions will be made for aircraft carrying dignitaries or emergency teams.

Italy [Images] has deployed thousands of police, snipers and armed skiers to patrol the slopes, venues and living quarters of athletes staying in Turin and villages in the nearby Alps.

Security forces will be on maximum alert during the Games to protect such dignitaries as Laura Bush and her daughter, Barbara, due in Turin on Friday after stopping in Rome and US air base in Aviano, Italy.

Security officials say they have had no specific terrorist threats against Turin in contrast to security concerns that dogged the Athens Games in 2004.

Anti-capitalists vowed on Tuesday to mount street demonstrations in Turin and try to disrupt Laura Bush's visit as part of a series of protests against the Games and their multinational sponsors, against the construction of a high-speed train between Italy and France [Images] and an anti-drug law.