A group of nearly 1,000 American victims of international terrorism is suing Clearstream Banking of Luxembourg, a unit of Germany's Deutsche Börse, for allegedly assisting Iran in fraudulently securing the release of $250m in frozen assets and in moving it out of the US financial system, according to legal documents recently unsealed by a federal court in New York.

The plaintiffs-family members of the 241 US servicemen killed in the 1983 bombing of a Marine Corps barracks in Beirut-are seeking the funds as partial payment of the $2.7bn that a federal judge in 2003 ordered Iran to pay the victims of the bombing. The judge ruled that Tehran had orchestrated the attack, at the time the largest terrorist act ever committed against US citizens. Iran has denied any role in the bombing.