TEHRAN: Iran has warned off foreign surveillance planes that have tried to approach its forces during air defence exercises on the Gulf coast, an Iranian military spokesman said on Wednesday.

"In the past three days, more than 12 warnings have been issued to aircraft from outside the region to refrain from approaching the airspace of the manoeuvre area," said Brigadier-General Abbas Farajpour Alamdari, quoted by the official news agency IRNA.

The semi-official news agency Tasnim said the warnings were given to U.S. Navy planes and drones that had approached the annual air drills.

There was no immediate U.S. reaction to the report.

Authorities have said that the recently delivered Russian S-300 surface-to-air defence system and locally made missiles, as well as radar and electronic warfare equipment, are among weapons tested in the war games stretching over three southern provinces.