Iran's leadership on Wednesday accused the United States of instigating political unrest after last week's disputed election that returned President Mahmoud Ahmadinejad to power amid accusations of vote fraud by his reformist rival.
Iranian officials summoned the Swiss ambassador — who represents U.S. interests in Iran in the absence of formal diplomatic ties between Washington and Tehran — to complain about "intolerable" meddling by the United States in Iran's internal affairs, the country's state television reported.
President Obama has said the U.S. respects Iran's sovereignty, but he has expressed "deep concerns" about the legitimacy of the election.
The Iranian television report came on the same day that thousands of people gathered in Tehran for a fifth straight day of protests by supporters of defeated presidential candidate Mir Hossein Mousavi. The opposition leader stepped up a challenge to the country's all-powerful Islamic leadership by urging another mass rally Thursday.
The call to protest defies Supreme Leader Ayatollah Ali Khamenei, who has warned Mousavi to pursue his demand for a new election through official channels and to halt demonstrations. Thursday's rally was also billed as a national day of mourning for seven people killed in clashes with pro-government militiamen earlier in the week.
"In the course of the past days and as a consequence of illegal and violent encounters" against protesters, "a number of our countrymen were wounded or martyred," Mousavi said on his Web site.
"We are after a peaceful rally to protest the unhealthy trend of the elections and realize our goal of annulling the election results," he said, asking his followers to wear black in memory of those slain and the alleged voting fraud.
Mousavi has charged Ahmadinejad with stealing the election, but the incumbent said the victory in Friday's vote was based on his government's "honesty and service to the people," according to a statement released by the semi-official ISNA news agency.
ISNA and the private ILNA news agency also reported that scuffles broke out between a reformist lawmaker and a hard-line legislator in an open session of the Parliament after they exchanged verbal attacks over the vote results.
On Wednesday, protesters — many clad in black and wearing headbands in the signature green of Mousavi's campaign — assembled in and around Tehran's Haft-e Tir square.
The opposition street protests, combined with dissent from powerful clerical and political figures, present one of the gravest threats to Iran's complex blend of democracy and religious authority since the system emerged from the 1979 Islamic Revolution that brought cleric Ayatollah Ruhollah Khomeini to power.
Blogs and Web sites such as Facebook and Twitter have been vital conduits for Iranians to inform the world about protests and violence after the government banned foreign reporters.
The Revolutionary Guard, an elite military force answering to Khamenei, said through the state news service that its investigators have taken action against "deviant news sites" that encouraged public disturbance and street riots.
Mousavi condemned the government for blocking Web sites, saying it did not tolerate the voice of the opposition.
Iran's most senior dissident cleric, Grand Ayatollah Hossein Ali Montazeri, said that the ruling Islamic system had no political or religious legitimacy because of widespread vote fraud. In a statement on his Web site, he said "no sound mind" would accept the results.
"A government that is based on intervening in [people's] vote has no political or religious legitimacy," said Montazeri, who had been set to succeed Khomeini as supreme leader, until he was ousted because of criticisms of the revolution.