Massive claim for US terror attacks

Those accused include the country of Sudan, three members of the Saudi royal family - including the Saudi defence minister - and various Islamic charities, in addition to seven financial institutions and the Bin Laden family's Saudi construction firm.

More than 600 family members, firefighters and rescue workers, calling themselves the 9/11 Families United to Bankrupt Terrorism, are seeking the money.

Stephen Push, who lost his wife in the attack, told the BBC the families had a strong case in the US but that it was a "multi-step process" and they would pursue it in other countries as well.

"The purpose of suing the Saudis who funded al-Qaeda is to try to help prevent the terrorists from getting access to financial resources they need to conduct future terrorist attacks," he said.

"We may be able to either convince them it's not worthwhile to fund al-Qaeda or perhaps obtain enough of their assets that they are no longer able to do so."

The suit was filed on Thursday morning in the US District Court of the District of Colombia.

Exposing financial support

BBC correspondents say the lawyers who are launching this case claim hundreds more families of victims of the attacks will join them.

So far the suit brings together families of victims from Argentina, Canada, France, Paraguay, South Africa and the United States.

They also accused the US Government of failing to pursue such institutions thoroughly enough because of lucrative oil interests.

Mr Push said the families had not received any financial support from the government and that the lawyers were working on a no-win no-fee basis.

'Complicated transactions'

The families acknowledged at a news conference held to publicise the suit that they faced huge odds, but said they were confident the US courts would uphold their claim.

"It's up to us, and I think we can do it," said Deena Burnett, whose husband was killed on Flight 93 which crashed into a field in rural Pennsylvania.

Lawyer Allan Gerson, who also worked on a lawsuit for families of victims of the 1988 Pan Am airline Lockerbie bombing, said that the suit was aimed at uncovering the complicated financial transactions which funded the 11 September attacks.

"We're trying to expose the extent, the depth, the orchestration, the financial support that terrorist organisations have received for perhaps a decade from various Saudi interests."