Protesters gathered in the streets, in shopping malls and outside the parliament building where they clashed with security forces.
After U.S. President Donald Trump withdrew from the Iran nuclear deal and re-imposed sanctions on Tehran-including on its oil industry and exports-expected to kick in later this year, the value of the Iranian rial has plunged to record lows against the U.S. dollar on the black market.
Now that the U.S. has withdrawn from the Iran nuclear deal, some sanctions are to be reimposed in August and November.
He said the protest was against "the high exchange rate, foreign currency fluctuations. goods being blocked at customs, and the lack of clear criteria for duties". Iran's semi-official news agencies Fars, ISNA and Tasnim described the protests at the Grand Bazaar as erupting after the Iranian rial dropped to 90,000 to the United States dollar on the country's black market, despite government attempts to control the currency rate.
Video footage of the unfolding demonstration obtained by RFE/RL showed hundreds of angry demonstrators marching in and around the Grand Bazaar, forcing shopkeepers to close their stalls.
Other videos appear to show the protestors chanting, "Death to dictator".
"Their demands are delivered through the chamber to the government, and these are being pursued by us", he said.
The protests come ahead of the renewed US oil embargo against Iran, which could capsize the nation's fragile economy.
Due to the economic protests, the authorities have closed Grand Bazaar, the main urban market of the capital.
At the end of a year ago, similar economic protests roiled Iran and spread to some 75 cities and towns, becoming the largest demonstrations in the country since its Y 2009 disputed presidential election.
A wave of demonstrations in December 2017-January 2018 rattled the regime and got worldwide media attention, but there have been few major disturbances reported in recent months.
Monday, June 25, in the protests in Tehran attended by at least two million people. The protests then spiraled out of control, with people openly criticizing Rouhani and Iran's supreme leader, Ayatollah Ali Khamenei.
Iran will set up a secondary currency market by the next week, Central Bank of Iran (CBI) Governor Valiollah Seif announced on Monday.
Meanwhile, some hard-liners have called for new elections or for Mr Rouhani's civilian government to be replaced by a military-led one.