The decision of the US and its allies last November to freeze the accounts of Barakat, the Somalia-based hawala money transfer group, was the highest-profile act so far in the financial war on terrorism.

Condemning the company as "the quartermasters of terror," Paul O'Neill called the group "a pariah in the civilised world." The US treasury secretary described it as a principal source of funding, intelligence and money transfers for the al-Qaeda network.

But US officials now say that Barakat's links to al-Qaeda are considerably less clear than those initial statements implied.

Barakat, also known as al-Barakaat, "is a piece of a larger mosaic," said a US treasury official, one in which al-Qaeda serves as "the umbrella organisation for a loose network of single-purpose, fundamentalist Islamic organisations."

The US action on Barakat underscores the controversey it may arouse in its continued efforts to shut off the financial pipeline to al-Qaeda.

While US allies in the Arab world, including the emirate of Dubai where Barakat was headquartered, have co-operated in shutting down the group, they are pressing the US for stronger proof before acting against others on a list of 168 groups and individuals so far targeted by the US.

Before the US and its allies shut it down last year, Barakat was the largest business group in Somalia, with subsidiaries involved in banking, telecommunications and construction. It had 60 offices in Somalia and 127 abroad in 40 countries, mostly involved in wiring money from expatriate Somalis living abroad to their families at home.

Its biggest asset was the large Somali diaspora in the US and Europe, from which US officials believe about $500m a year flowed back to Somalia via its banking operations in Dubai.

The US believes that about five per cent was skimmed from each of these transactions in commissions, a fee low enough to attract Somalis eager to send funds home but still high enough to provide at least $15m to $20m annually that was allegedly diverted for terrorist causes.

It is not clear that Barakat has ever channelled money directly to al-Qaeda. However, the US says it acted against Barakat because of Barakat's links with a militant Somali group - al-Ittihad al-Islami - that it believes is part of this larger network of terror.

"[But] there is no reason to make a distinction" between al-Qaeda and al-Ittihad, said the US official.

US officials also say that the Barakat network, which included internet communications, provided "logistical support" for Bin Laden and al-Qaeda cells worldwide, though they have not elaborated on what sort of support was provided.

Ahmed Nur Jumale, the chairman of Barakat who set up the group in 1989, said yesterday that US officials have seen the company's accounts and that funds leaving Barakat offices tally with those arriving in Somalia, suggesting that there is no evidence of diversion. Anyway, he said, "$20m is more than we could make in 20 years."

Mr Jumale also said that the US had exagerrated the role of al-Ittihad al-Islami, which could not be a conduit to al-Qaeda as the US asserts, because it is barely functioning. "There is at this time no al-Ittihad al-Islami in Somalia. It is discussed as if it is powerful and exisiting, when actually it is dead," he said.

The US, however, discounts those denials, saying that Mr Jumale's links with Mr bin Laden go back to Somalia in the early 1990s. Mr Jumale is alleged by the US to have been a close associate of Mohamed Farah Aideed, the Somali warlord who forced the humiliating withdrawal of US peacekeeping forces from Somalia after a firefight in 1993 left 18 American soldiers dead.

All three, the US says, were united by a similar desire to drive the US military out of the region.

This account, however, raises as many questions as it answers.

First, the only reasonably clear sign of an al-Qaeda presence in Somalia at that time amounted to a short, and apparently insignificant visit in 1993, by an activist - not Mr bin Laden himself.

Further, while Mr bin Laden and Gen. Aideed were similarly opposed to the US, Gen. Aideed always portrayed himself as a staunch opponent of the radical Islamist groups. His militiamen fought bloody battles with al-Ittihad al-Islami on several occassions, Gen. Aideed said in interviews in the mid-1990s.

Finally, al-Ittihad itself has had only a fleeting presence in Somalia, occassionally seizing control of small towns along the country's borders or on the coast, but rarely holding them for very long.

In spite of all this, the US says the Barakat case has demonstrated the unexpected scope and scale of al-Qaeda's fund-raising efforts. Its officials believe Barakat reveals how Mr bin Laden succeeded in drawing on a disparate group of Islamic radicals united only by their hatred of the US.