DUBAI: Iran said it would deal decisively with any foreign encroachment into its airspace, an apparent warning to the United States after one of its surveillance drones was targeted by Iranian warplanes last week.

On Thursday U.S. officials said the unarmed Predator drone was in international airspace when Iranian warplanes opened fire on it on Nov. 1. The aircraft was not hit.

The intercept was the first time Tehran had fired at an unmanned U.S. aircraft in their 33 year stand-off.

"The defenders of the Islamic Republic will respond decisively to any form of encroachment by air, sea or on the ground," Fars news agency quoted General Massoud Jazayeri, a senior armed forces commander, as saying on Friday.

"If any foreign aircraft attempts to enter our airspace our armed forces will deal with them," he said. Jazayeri did not mention the drone incident specifically.

According to the Pentagon, two Soviet-designed SU-25 aircraft intercepted the Predator drone over Gulf waters about 16 nautical miles off the Iranian coast. After firing at the drone they followed it for several miles as it moved farther away from Iranian airspace.

Washington has issued a formal protest to the Iranian authorities via diplomatic channels.

Details of the incident emerged ahead of large-scale air defence drills due to start across several provinces in eastern Iran this week.

The "Velayat 4" manoeuvres will be jointly held by the regular armed forces and the Islamic Revolutionary Guard Corps and will involve testing new radar and surveillance equipment, military commanders say.