The US State Department said on Saturday it "strongly condemns" the arrest of protesters in Iran, where dozens were detained during demonstrations against high prices and unemployment.
The State Department is monitoring the protests, and urged "all nations to publicly support the Iranian people and their demands for basic rights and an end to corruption," spokeswoman Heather Nauert said in a statement.
"Iran's leaders have turned a wealthy country with a rich history and culture into an economically depleted rogue state whose chief exports are violence, bloodshed, and chaos," she said.
"As President Trump has said, the longest-suffering victims of Iran's leaders are Iran's own people."
Hundreds took to the streets of Mashhad and other cities on Thursday, and an Iranian official said that 52 were arrested in Mashhad.
The head of Mashhad's revolutionary court, Hossein Heidari, said people were arrested for chanting "harsh slogans," the Fars news agency reported.
Protests spread to the capital Tehran and Kermanshah on Friday, although numbers reportedly remained small, in contrast with the "Green Movement" opposition protests in the aftermath of the 2009 election.