"Police managed to discover a fraud case and arrest a European national who scammed 120 billion rials" since 2015 through claiming to invest in agriculture, said the force's spokesman Brigadier-General Ahmad Noorian.

Currently 120 billion rials amounts to around $1 billion, or nearly 900 million euros, under the unofficial exchange rate in the Iranian capital.

The accused had come under suspicion when authorities discovered forged documents, the spokesman was quoted as saying in a report by the website of state television.

The European national was then identified as a butcher by profession who had no capital and was "linked to an international conman wanted by Interpol".

State news agency IRNA said the accused had been arrested in the city of Birjand, South Khorasan, and had an accomplice who was also European.

They had presented themselves as investors in the wake of the deal -- known formally as the Joint Comprehensive Plan of Action (JCPOA) -- that gave Iran relief from sanctions in return for curbs on its nuclear programme.

"The investigation indicated that after the JCPOA, two European nationals introduced themselves to Iran's embassy" in a Gulf Arab country, said South Khorasan police chief Majid Shoja.

They were introduced to authorities in the province and then "encouraged one of the domestic investors to invest", he was quoted as saying by IRNA.

"The Iranian partner incurred a lot of expenses," said the police chief.

"In addition to accommodation, health care, business tickets for flights... and the provision of an office with the most up-to-date facilities, (the Iranian partner) paid about 120 billion rials into the accounts of these two European nationals."

The partner later lodged a complaint and one of the European nationals who was in Iran was detained, he added.