A team from the Overseas Development Administration (ODA), the first official aid organisation to visit the area in recent years, found evidence that the Marsh Arabs, much of whose ancient homeland has been drained by the Iraqi government, are being poisoned by chemicals put into their water supply by the authorities.
''I discovered symptoms of chronic long-term poisoning among many Iraqi women, young men and children,'' said Mukesh Kapila, a doctor who led the ODA mission to south-western Iran, where thousands of Iraqi refugees are seeking sanctuary. ''I also saw scars from bullets which people said had been fired by Iraqi soldiers. There is no doubt that what is happening to the Marsh Arabs in Iraq amounts to genocide.''
In recent years, up to half a million people are estimated to have fled the marshlands, the largest wetland ecosystem in the Middle East and home to the Marsh Arabs for nearly 5,000 years. According to an Exeter University report published this year, the marsh region - an area slightly smaller than Wales - will disappear within the next decade or so if the Iraqi government continues to drain it.
Already, between a half and three-quarters of the surface area has been drained by huge engineering works.
Iraq claims this is for ''agricultural purposes'', but most observers believe it is part of Saddam Hussein's campaign to crush Shia insurgents operating out of the marshes. Draining has allowed the Iraqis to penetrate Shia strongholds and use heavy artillery.
''The flood of Iraqis into Iran is fast becoming a crisis,'' warned Dr Kapila, who was invited by Iran to assess the humanitarian aid needs of the refugees in south-western Iran. ''At the main border crossing of Himmet we saw more than 3,000. The Iranian local authorities reckon there are another 20,000 waiting to cross and as many as a quarter of a million preparing to come into Iran over coming weeks.''
About 150,000 people, half of them Marsh Arabs, are believed to have fled into Iran from Iraq in the past two years, bringing the number of Iraqi refugees in Iran to about 650,000. About a third of these live in camps along Iran's western border. Although generous to Iraqi refugees in the past, Tehran now appears to be clamping down on the numbers coming across from Iraq.
''In addition to the Marsh Arabs, we saw many people from Baghdad and northern Iraq coming over the border,'' Dr Kapila said. ''There seems to be a rapid deterioration of conditions inside Iraq. Many reported the looting of food stores in the capital. People appear to be fleeing for economic as well as political reasons.''
Dr Kapila reports a high proportion of women and children among the Marsh Arabs crossing into Iran. He concludes that many of the menfolk have been captured or killed by the Iraqi army.
''Of the 3,000 people we saw stranded in no man's land, about half were children. Many were suffering from diarrhoea and dysentery. There is also a real danger of cholera.''
The ODA is considering more than pounds 1m of emergency assistance to Iraqi refugees in Iran. On Tuesday Baroness Chalker, the Minister for Overseas Development, is to present a first cheque of pounds 85,000 to the Conservative MP Emma Nicholson, founder of Assist Marsh Arabs and Refugees and chairwoman of the Iraq all-party committee in the Commons.