South Korea transferred frozen Iranian funds to Switzerland's central bank last week for exchange and transfer to Qatar, South Korean media reported on Monday.

The Swiss National Bank plans to exchange its $6 billion holdings in won for dollars and then euros in the currency market, converting about 300 billion won ($223.85 million) to 400 billion each day for next five weeks, Yonhap Infomax reported, citing an unnamed currency market source.

An official at South Korea's finance ministry declined to confirm the report, citing the legal and diplomatic sensitivity of the matter.

Iran and the United States recently reached an agreement in which five US citizens held hostage in Iran would be released while Iranian assets in South Korea would be unfrozen and sent to an account in Qatar that Iran could access. The Biden administration insists that the funds can only be used by Iran to purchase food, medicine and other humanitarian needs, but the Iranian foreign ministry and officials have insisted there would be no restrictions on the funds.

Iranian President Ebrahim Raisi said last week that the released assets would be used to enhance domestic production.

The deal has led to a lot of criticism in the United States by those who say the $6 billion is essentially a ransom paid for five hostages and it will only encourage Iran and other actors to detain Americans and demand money or concessions. Twenty-six Republican Senators have written to President Joe Biden demanding clarifications. Critics also argue that the money will provide Iran with the ability to spread its terror activities and other malign acts.