"We could smell something strange like apples," recalls Aras Abed Akra. "Down in our shelter we felt short of breath. A soldier went out and next door he saw that the caged birds of our neighbour were all dead."

Gently prompted by a doctor to relive his experiences as a form of therapy, Mr Akra slowly describes the events of March 1988, when Iraqi jets bombed the northern Kurdish town of Halabja, the most devastating poison gas attack on a civilian population in history.

The first wave of aircraft dropped conventional bombs, sending people down into basements.

With the next wave came innocent-looking streamers, which, with hindsight, people realised were dropped to gauge wind speed and direction.

"We stayed in the shelter until evening, but then I just wanted to escape," continues Mr Akra, then 22. "We wrapped our faces in wet towels. It was hard to breathe. One friend became blind immediately when he removed his towel. We got confused and lost, couldn't see more than a metre ahead."

Halabja was singled out for attack because the local Kurdish population had sided with Iran in the eight-year war with Iraq that began in 1980.

Mr Akra was picked up by the Iranians and, like many other victims, taken to hospital inside Iran. He returned to Halabja in search of his family. "I saw over 200 bodies in just 100 metres. There was a terrible smell from the chemicals and the corpses. I went to the shelter. I first saw my grandmother. She had swollen up. Then I saw the blackened face of my mother and I lost consciousness."

Some months later Mr Akra was captured by the Iraqi army and conscripted. Bitterly, he recalls he was posted to a chemical warfare administration unit.

Kaveh Golestan, an Iranian photographer, was about 8km outside Halabja with a military helicopter when the Iraqi MiG-26s flew in. He was in a village that had already been gassed, empty of people but full of dead sheep.

The journalists had chemical suits, syringes for drugs to counteract the effects and masks - except that the filter in the mouthpiece was missing.

"It was not as big as a nuclear mushroom cloud, but several smaller ones: thick smoke," says Mr Golestan, winner of a Pulitzer award.

Nervous of being caught in the attack, their pilots flew back to Iran.

They returned the next day. Mr Golestan had seen gas attacks before, when he was at the frontline, but this was different.

"It was life frozen. Life had stopped, like watching a film and suddenly it hangs on one frame. It was a new kind of death to me. You went into a room, a kitchen and you saw the body of a woman holding a knife where she had been cutting a carrot.

"The aftermath was worse. Victims were still being brought in. Some villagers came to our chopper. They had 15 or 16 beautiful children, begging us to take them to hospital. So all the press sat there and we were each handed a child to carry. As we took off, fluid came out of my little girl's mouth and she died in my arms."

According to Christine Gosden, a professor of medical genetics at Liverpool University, the Halabja attack involved a cocktail of chemical agents, including mustard gas, and the nerve agents sarin, tabun and VX.

More than 14 years have passed, but still the Kurds of Halabja are suffering.

Dr Gosden says the occurrences of genetic mutations and cancer in Halabja "appear comparable with those who were one to two kilometres from ground zero in Hiroshima and Nagasaki."

Adil Kerem Fatah, director of the local hospital, is convinced that higher incidences of cancer and birth defects in the region are linked to the use of chemical agents, but he is exasperated over the lack of aid for research or treatment.

Dr Fatah has carried out his own surveys which, he says, show higher incidences of cancer, especially of the breast and colon, as well as infertility, congenital birth defects, diseases of the respiratory system and severe eye problems.

His hospital performed 108 deliveries in April and among them were four cases of anencephaly, where part of the brain is missing - a rate that is far higher than the international norm.

The people of Halabja, under the control of autonomous Kurdish administrations since 1991, find it ironic that the US now condemns Saddam Hussein's regime as forming part of an "axis of evil".

Back in 1988, the US and much of Europe had tilted heavily towards Iraq in its war with Iran. There was little international reaction to the attack, which the Kurds say killed some 5,000 people.

Despite its isolation, Halabja is slowly recovering. Wedged at the end of a broad valley with marshlands and lakes, the fields are fertile and shops are full of local produce from soil that has never been thoroughly tested.

Graveyards, just a jumble of small mounds marked by jagged rocks, are disappearing among fields of wheat and barley. Stone houses still lie in ruins.

Apart from the hospital patients like Mr Akra, seeking treatment for trauma and physical disorders, the only obvious sign of the tragedy is a simple memorial on the main road, two prone figures in stone, of a man in a last futile attempt to shield his grandson.