The files listed the nationalities and biographical details of more than 700 fighters who crossed into Iraq from August last year, around half of whom came to the country to be suicide bombers, the New York Times reported today.

In all, 305, or 41%, of the fighters listed were from Saudi Arabia. Another 137, or 18%, came from Libya. Both countries are officially US allies in anti-terrorism efforts.

In contrast, 56 Syrians were listed and no Lebanese. Previously, US officials estimated that around a fifth of all foreign fighters in Iraq came from these two countries.

US officials have also long complained about Iranian interference in the affairs of its neighbour, accusing Tehran of shipping weapons for militants over the border. However, any assistance does not appear to extend to people, the paper said, reporting that, of around 25,000 suspected militants in US custody in Iraq, 11 were Iranian. No Iranians were listed among the fighters whose details were found.

The information came from files and computers seized in September when US forces raided a camp in the desert near Sinjar, a small town in north-west Iraq, close to the Syrian border. It was believed the camp was the base for an insurgent cell responsible for smuggling the vast majority of foreign fighters into Iraq.

The files also gave details of 68 Yemeni nationals, the third-biggest source. There were 64 fighters from Algeria, 50 from Morocco, 38 from Tunisia, 14 from Jordan, six from Turkey and two each from Egypt and France.

According to the newspaper, US officials believe the raid stemmed the flow of foreign militants into Iraq, which dropped to around 40 in October, down from a peak of more than 100 a month in the first half of this year.

Last month there were 16 suicide bombings in Iraq, sharply down from a peak of 59 in March. According to the report, the US military believes 90% of such attacks are carried out by foreigners.

However, US officers fear this effect may be temporary. "We cut the head off, but the tail is still left," a senior military official told the newspaper. "Regeneration is completely within the realm of possibility."

The US has previously estimated the nationalities of fighters crossing over the Syrian border into Iraq, but the seized files give a more complete picture.

While Saudi Arabia is a long-term US ally, its nationals form the nucleus of al-Qaida; 15 of the 19 September 11 attackers were from the country.

And while Libya was listed by the US as a state sponsor of terrorism, it was removed last year after the countries restored full diplomatic relations.