The riyal lost about a quarter of its value in the last six months to reach $ 50,860 riyals, according to the Financial Information Market, a reliable website tracking open market volatility.
The gap continued to widen with the official exchange rate of 37686 riyals on Monday.
The Iranian government took tough measures last month to stem the devaluation of the local currency on the open market, where it arrested foreign currency traders, froze speculators’ accounts, raised interest rates and bought millions of dollars in an effort to curb its rise.
Many analysts believe the United States will withdraw from the nuclear deal reached with Iran in 2015 when it is due to be renewed in May, which means re-imposing sanctions, which have greatly affected the Iranian economy.
Iranian officials have complained that citizens are racking up billions of dollars at a time when local banks are short of liquidity.
The devaluation of the currency is a key problem for the government of President Hassan Rowhani, who was hoping to attract large foreign investment after the nuclear deal.
The collapse of the currency would be another expulsive factor for potential investors, who already face major hurdles as a result of US sanctions unrelated to the remaining nuclear file.