"The Russian embassy expressed bewilderment and asked that from now on Russian specialists at Bushehr be informed in advance about that type of activity," foreign ministry spokesman Mikhail Kamynin was quoted as saying.

Kamynin said the live-fire air defence exercise took place Friday "in the immediate vicinity" of the almost-completed nuclear power station at Bushehr.

Russia's nuclear power agency, Rosatom, said the military exercise "stirred up excessive tension around the site," RIA Novosti news agency reported, citing a spokesman.

Bushehr is due to be Iran's first nuclear power station. Russia has also sold Iran sophisticated weaponry, including 29 TOR-M1 anti-aircraft missile systems.

Washington is leading international pressure against Iran's development of a nuclear power programme and says that Russia should have cancelled the TOR-M1 sales because of the international tensions.