The remarks by Gen. Hamid Arjangi, a spokesman for the exercise, were the first Iranian claim of an intrusion. Initially, he had only said that foreign reconnaissance planes had approached Iran's air space.

Arjangi said Iran's radar stations and observation posts picked up on the planes entering Iranian airspace during the five-day drill, which started on November 16.

 "There were six cases of intrusion by unidentified planes into the country," Arjangi was quoted as saying by the official IRNA news agency. "In all six cases, air force jet fighters took off and carried out interception operations ... artillery systems were alerted, targets were identified and necessary warnings were given."

The Iranian exercise is meant to showcase the country's capabilities in defending its nuclear facilities from possible attack.

It followed an announcement by the Iranian Air Force saying its troops earlier this year conducted an exercise at several facilities - the uranium enrichment plant at Natanz, the under-construction enrichment site at Fordo, the nuclear conversion facility near Isfahan and the Bushehr nuclear power plant.