American soldiers suffering from post-traumatic stress disorder after their return from the war in Iraq are being given a treatment psychiatrists have long practised - confront the object of their fears.

But this time, their re-visit to the war ravaged country is done in the safety of a clinic in America where they are led through the explosions, fire and smoke via virtual reality.

This system, developed by researchers sees the soldiers wearing goggles and headphones to be transported through the sights, sounds and even smells that once traumatised them in Iraq.

Albert "Skip" Rizzo, research assistant professor at the Institute for Creative Technologies at the University of Southern California, which has developed this treatment with the U.S. Navy's Office of Naval Research, says this treatment is working, according to a report in computerworld.com.

Since clinical trials started late last year, six soldiers have been treated, Rizzo said. Four have seen "dramatic improvements," and one of the treated soldiers has returned to Iraq, with another to go back soon.

The virtual reality system is based on a video game called Full Spectrum Warrior that was developed by the Army as a training tool. The researchers added graphics, sounds, vibrations and smells to the original game to create various scenarios replicating those experienced by soldiers in Iraq, Rizzo said.

The scenarios include soldiers being shot at by insurgents, crashing in a helicopter or witnessing a bomb exploding or a fellow soldier being shot. To help make the experience more real, the platform where the soldier sits can vibrate during a humvee ride and provide the smell of human sweat, gunpowder or burning rubber.

"We're basically trying to use computer systems to create as immersive an environment as we can," he said. "The sense of smell is directly tied to areas of the brain that are responsible for memory and emotion."

Using a tablet PC, the person treating the soldier can gradually add more frightening stimuli, so that "a person experiences a little bit of anxiety, and they stick with it and talk about it, and eventually that anxiety extinguishes," Rizzo said.

Soldiers have told the researchers that they want even more realism in this programme and have requested for the addition of more wounded people when a vehicle explodes or a building blows up, Rizzo said. They also plan to add specific emerging attack scenarios such as insurgents coming out of houses or attacking from rooftops and bridges.