Iran has executed a trader dubbed the "Sultan of Coins" for hoarding gold coins and manipulating currency markets as the country faces fresh United States sanctions and a deepening economic crisis.

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

Vahid Mazlumin, known as the "sultan of coins", and his accomplice Mohammad Ismail Qasemi, also known as Mohammad Salem, had been convicted of "spreading corruption on earth", a capital offense under the Islamic law.

The UN, Western countries, and global human rights groups have expressed concerns about the rising number of executions and reported torture incidences in Iran for a variety of alleged offenses, including issues related to religious freedom, women's rights, and economic protests.

They were put to death after the Supreme Court upheld their death sentences and the legal processes were completed, Tasnim reported.

Mazloumin didn't hold a permit to trade gold and foreign currency, yet had formed the largest illegal network in that area, according to state-run Fars news agency.

Police said Mazloomin had "amassed around two tonnes of gold coins" by the time of his arrest on 2 July.

The Islamic Revolutionary Court - which deals with national security issues - had sentenced the two men to death in October. Dozens of other people have also been sentenced to prison terms after convictions on similar charges.

The Iranian rial plunged to a record low against the U.S. dollar on the unofficial market after President Donald Trump in May withdrew from a deal on Tehran's nuclear program.

Growing public anger over high inflation, economic hardship, and widespread corruption has led to sporadic street protests in Tehran and other cities, with the demonstrators chanting antigovernment slogans.