DUBAI (REUTERS) - A first tranche of US$550 million (S$701 million) in sanctions relief agreed under an interim nuclear deal has been paid into an Iranian Central Bank account in Switzerland, the official IRNA news agency said on Monday.

Quoting an informed source, the agency reported: "$550 million in frozen Iranian assets (were) transferred to Iran's Central Bank account in Switzerland.

The agency said the money was a first instalment of US$4.2 billion in blocked Iranian oil revenue that is to be made available to Iran under the Nov 24 deal.

That agreement is designed to curtail Iran's nuclear activities for a six-month period beginning on Jan 20 in exchange for sanctions relief from six major powers: Britain, China, France, Germany, Russia and the United States.

Under the accord, Iran agreed to curb its most proliferation-sensitive nuclear activity - higher-level uranium enrichment - in return for some relief from Western sanctions.

The agreement aims to give the two sides six months to reach a comprehensive deal to address all questions about whether Iran seeks nuclear arms.

Iran says its program is for solely peaceful purposes such as generating electricity and medical isotopes.

Among the total sanctions relief over the six months, US$4.2 billion is in the form of access to currently blocked Iranian revenues held abroad.

In January, a US official said access to some of those funds depended on Iran keeping its commitment to dilute half of its 20 per cent enriched uranium to no more than 5 per cent enriched uranium.