ANKARA (Reuters) - The leader of Friday prayers in Tehran called for calm and fortitude after days of protests by the capital’s Grand Bazaar traders fuming over the plunging value of Iran’s currency and rising prices, the semi-official Fars news agency reported.

Three days of protests in Tehran and other cities began on Sunday when hundreds of traders in the bazaar - the hub of merchants who backed Iran’s 1979 Islamic Revolution that ousted the longtime monarch - closed their shops to voice their anger at currency plunges.

Iran’s rial has lost 40 percent of its value since President Donald Trump’s decision on May 8 to pull the United States out of Iran’s 2015 nuclear deal with world powers and reimpose tough economic sanctions on Tehran.

“Our enemies want to harm us by creating chaos...Remain calm and resist the economic hardship... We will overcome all difficulties if we remain united and resist the pressure,” Shi’ite cleric Kazem Seddighi told worshippers in Tehran.

Thousands of people including merchants took to the streets on Sunday and marched toward the parliament building where they shouted slogans against Iranian authorities. Riot police clashed with protesters and fired tear gas to disperse the crowds.

The protests resembled nationwide demonstrations in January that were originally sparked by economic hardships but turned political. However, the protests earlier this year took place largely in Iran’s provinces rather than in Tehran.

Trump has ramped up pressure on U.S. allies to cut off purchases of Iranian oil, which accounts for 60 percent of the Islamic Republic’s income.

Watching their savings dwindle and shopkeepers hold onto some of their goods, Iranians fear new sanctions will also see sharp rises in the price of food including rice, bread and dairy products.

“Those hoarders are hurting the economy...Bring the goods to your shops from storages,” Seddighi said.

Most international sanctions imposed on Iran were lifted in early 2016 under the nuclear deal that saw Iran curbing its disputed nuclear program under close U.N. monitoring.

The bazaar strike was the biggest sign of domestic disquiet in Iran since Trump ditched the nuclear deal. The pact was the centerpiece of President Hassan Rouhani’s promise to modernize Iran’s economy that won him two landslide elections but has yet to bring widespread tangible benefits for many Iranians.