Iran did not provide evidence for its accusation, which evoked memories of the C.I.A.’s role in a 1953 coup that overthrew the democratically elected government of Mohammed Mossadegh.
Iran’s mission to the United Nations also sent a letter to the United Nations Security Council on Wednesday complaining about “acts of intervention” by the administration, citing President Trump’s Twitter posts in support of the protests.
The Islamic State also played a role, Mr. Montazeri said, without explaining precisely how. He also called on clerics in the holy city of Qum to support the judiciary in a permanent ban on the messaging app Telegram, now closed in Iran.
Government officials also blamed internal enemies for instigating the protests, with the leader of the Islamic Revolutionary Guards Corps seeming to imply that a former hard-line president, Mahmoud Ahmadinejad, was involved.
Whatever Mr. Ahmadinejad’s role, Iran’s reformist faction has accused hard-liners in the city of Mashhad of organizing the first protests to create political problems for Iran’s moderate president, Hassan Rouhani. And hard-liners have, in turn, accused Mr. Rouhani of leaking secret parts of his proposed budget, including details of the country’s religious institutes, in a calculated move to turn ordinary people against religious institutions.
“They all blame each other,” said Nader Karimi Joni, a reformist journalist. “What else can they do?”
The death toll from the clashes rose to at least 21, and in the central province of Esfahan, a police officer was reported killed.
The United States State Department said on Thursday: “We condemn in the strongest possible terms the deaths to date and the arrests of at least one thousand Iranians,” it said, adding, “To the regime’s victims, we say: You will not be forgotten.”
Unrelated to the protests, the United States Treasury Department imposed sanctions on five Iranian entities over their involvement in developing ballistic missiles, and Treasury Secretary Steven Mnuchin said additional sanctions “targeting human rights abuses are coming.”
The protests, meanwhile, seemed to be winding down, though there is no sure way to tell. Fewer videos of what seemed to be demonstrations appeared on social media on Thursday. But many sites have been blocked, possibly obscuring the true extent of the protests.
Iran’s government routinely filters websites and apps it deems…