A top court in Luxembourg has officially blocked a long-running request by the US administration to seize $1.6 billion worth of Iranian cash assets as compensation for alleged terror victims of the September 11, 2001 attacks in the United States.

The Luxembourg Court of Cassation announced in an official statement on Monday that the appeals court has found the US seizure demand "inadmissible" and in violation of the Luxembourg’s national law since the type of account, in which the cash is held in the European country, is "unseizable."

The funds are currently kept in the Clearstream clearing house, a financial company owned by Deutsche Boerse based in Luxembourg.

The statement added that a Luxembourg district judge had blocked the transfer of funds and ruled that Clearstream would be subject to a daily fine of $1.09 million if it moved the money.

This came after Iranian President Hassan Rouhani said a day earlier that the country had won a legal "victory" over the assets that had long been frozen on a US request in Luxembourg.

"$1.6 billion of our money was in Luxembourg and the Americans had put their hands on it," Rouhani said, adding that after trying for months, "We succeeded some and freed this money from the Americans' grasp."

Back in 2012, a New York court claimed there was evidence to show that Iran provided “material support and resources” to al-Qaeda operatives that carried out the terrorist attacks in the US in 2001.

The New York court awarded the plaintiffs damages of over $7 billion.

Iran has denied any links to al-Qaeda or any involvement in the 9/11 attacks.

Tensions have escalated between Washingtonian and Tehran particularly after President Donald Trump reinstated US sanctions on Iran in May 2018 after he unilaterally left the 2015 nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), signed between Iran and major world powers.

The International Court of Justice (ICJ) — known as the World Court — has ordered the US to lift the sanctions it has illegally re-imposed on humanitarian supplies to Iran.