Iran has launched the main phase of its largest army exercise ever.

Officials said the main stage of Payrovan-i Vilayat-2004 took place on Wednesday in southwestern Iran near the Iraqi border. They said air and ground units launched a night-time offensive on a mock enemy in a demonstration of Iran's rapid deployment capability.

Iranian ground forces also practiced defense against a chemical weapons attack. Troops were said to have employed protective suits and tested decontamination equipment.

So far, the exercise, which began on Dec. 3, has contained three phases, Middle East Newsline reported.

They included the use of infantry, artillery, and armored units in an offensive backed by fighter-jets and helicopters. At the same time, engineering and bridging units erected bridges for infantry crossing.

The exercise has taken place in an area of 100,000 square kilometers in the provinces of Hamedan, Ilam, Kermanshah, Khuzestan, and Luristan. Brig. Gen. Nasir Mohammadifar, commander of Iran's regular army, said artillery, missile and electronic warfare units were being trained in what he termed asymmetric warfare.

Mohammadifar said this enabled steady attacks on the enemy "without the enemy knowing from where the blows were coming from." He said the exercise contained 10 infantry divisions.

"Many tactics of asymmetrical wars were used in that stage of the war game and several surface-to-air missile and Naze at surface-to-surface missile were fired on the enemy targets," the official Iranian news agency, Irna, said.

Officials said the war maneuvers have come under scrutiny from the Iranian leadership On Wednesday, Iranian supreme leader Ali Khamenei said the exercise would increase the combat readiness combat and support units and said such maneuvers should be a priority by both the regular army and the Iranian Revolutionary Guard Corps.