Iran has executed the so-called "Sultan of Coins" and his accomplice for hoarding gold coins and other hard currency, signalling zero tolerance as it tries to shore up its currency in the face of an economic crisis.

State TV reported that Vahid Mazloumin and his accomplice, Mohammad Ismail Ghasemi, were hanged early on Wednesday (local time).

They were convicted of manipulating coin and hard currency markets through illegal and unauthorised deals, as well as smuggling.

An unspecified number of other accomplices went to prison.

Iran detained Mr Mazloumin, 58, in July for hoarding 2 tonnes of gold coins.

Iranians have stocked up on gold coins and other safe-haven investments as the local currency has plummeted in recent months, amid renewed US sanctions following President Donald Trump's withdrawal from the 2015 nuclear deal in May.

The Iranian rial has plunged to 135,000 to the US dollar from last year's rate of about 40,500.

Last week, President Hassan Rouhani said the Islamic Republic's already ailing economy is in a "war situation".

Sporadic protests over the deteriorating economy have erupted in recent months.

The value of the Iranian rial has plunged over the last year. ( Reuters: Raheb Homavandi )

AP