While London paid Tehran $530 million to free two British dual nationals, it is not clear if the cash is at Iran’s disposal, or has strings attached to it.

The Iranian Foreign Ministry Spokesman Saeed Khatibzadeh insisted that the funds have been put at the disposal of Iran and Tehran has full control of it. "It is only Iran and not any other party including the UK that can determine how the money is going to be spent."

The British side has offered a different account about the payment. According to a statement by the British Foreign Secretary Liz Truss, "The IMS debt has been settled in full compliance with UK and international sanctions and all legal obligations. These funds will be ring-fenced solely for the purchase of humanitarian goods."

The Guardian had earlier reported that that the sum will be spent under the supervision of Switzerland.

But Russ also said: "Last December I met Omani Foreign Minister Badr to secure Oman’s diplomatic assistance. We are grateful to our friends in Oman for their support in securing the return of our nationals."

Meanwhile, other sources in London told Iran International TV that the sum is at the disposal of the Central Bank of Oman as a credit line and will be paid for purchases made by Iran and verified as being spent for humanitarian needs.

Yet another source told the IITV, that the US National Security Adviser Jake Sullivan has played a constructive role in facilitating the payment for humanitarian reasons while Iran is being sanctioned by the United States.

The release of dual nationals Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori has been hotly debated in Iran, with hardliner media claiming victory for forcing the UK to pay and their opponents questioning the detention of the dual nationals.

IRGC-linked Fars and Tasnim news agencies as well as other conservative media outlets including Mehr news agency reported on Wednesday that the prisoners were released only after the United Kingdom made the payment to Iran. But Foreign Minister Hossein Amir-Abdolahian has said that that there was no link between the release of the detainees and the money paid.

Amir-Abdollahian also reiterated in an interview with IRNA that money changed hands between the UK and Iran a few days prior to the prisoners' release and although the payment and the release of prisoners took place within a short period, the two events were not connected.

On Thursday, hardline daily Kayhan ruled out the Iranian Foreign Minister's statement and wrote that the UK was "forced" to pay back its $530 million debt.

The official news agency IRNA insisted that the release of the two prisoners was based on humanitarian reasons and a decision made just before the Iranian New Year (Nowruz) and the birthday of the 12th Shiite Imam.

However, former lawmaker Ali Motahari wrote in a tweet that "If Iranian officials are telling the truth about releasing Zaghari-Ratcliffe for humanitarian reasons, and her imprisonment and release had nothing to do with the UK's debt to Iran, they should explain what she had done to deserve spending 6 years in jail in Tehran."

Some Iranian news outlets including Etemad Online reported that a third British Iranian prisoner Morad Tahbaz was also granted furlough and that he is out of jail and with his family in Tehran. The furlough was reportedly part of the deal that led to the release of the other two prisoners. Why the UK did not demand full freedom for all detainees, having paid hundreds of million of dollars, is not clear.