TEHRAN, Iran (AP) - Iran directly accused the United States of meddling in the deepening crisis over a disputed presidential election and broadened its media clampdown Wednesday to include blogs and news Web sites. But protesters took to the streets in growing defiance of the country's Islamic rulers.
The sweep of events - including more arrests and a call for another mass opposition march through Tehran - displayed the sharpening attacks by authorities but also the unprecedented challenges directed at the very heart of Iran's Islamic regime: its supreme leader and the cleric-run system.
Any serious shift of the protest anger toward Iran's non-elected theocracy would sharply change the stakes. Instead of a clash over the June 12 election results, it would become a showdown over the core premise of Iran's system of rule - the almost unlimited authority of the clerics at the top.
For the moment, however, both sides appear to be using the same tactics since the disputed results showed hard-line President Mahmoud Ahmadinejad as the landslide winner.
Opposition leader Mir Hossein Mousavi called for another mass rally Thursday in open defiance of Iran's most powerful figure, Supreme Leader Ayatollah Ali Khamenei, who has urged the nation to unite behind the Islamic state.
Authorities rounded up perceived dissidents and tried to further muzzle Web sites and other networks used by Mousavi's backers to share information and send out details of Iran's crisis after foreign journalists were banned from reporting in the streets.
Officials also stepped up claims that foreign hands have been behind the unrest.
A statement by state-run Press TV blamed Washington for "intolerable" interference in the bloody showdown over allegations of vote-rigging and fraud. The report, on Press TV, cited no evidence.
It said the government summoned the Swiss ambassador, who represents U.S. interests in Iran, to complain about American interference. The two countries severed diplomatic relations after the 1979 Islamic Revolution.
The State Department this week asked Twitter to postpone a scheduled maintenance shutdown of its service to keep information flowing from inside Iran, three U.S. officials said, speaking on condition of anonymity because of the sensitivity of the situation.
A State Department spokesman said Washington was withholding judgment about the election and was not interfering in Iran's internal affairs. President Barack Obama has offered to open talks with Iranian leaders to end a nearly 30-year diplomatic freeze.
For nearly that entire time, Iran's ruling clerics held uncontested power over nearly every critical decision, including possible talks with Washington. But the upheavals have pushed them into unfamiliar territory.
Khamenei and his inner circle have been drawn into a messy and public crisis - with the election dispute even bringing possible splits within the theocracy.
Chances for a full-scale collapse are considered very remote. The ruling clerics still have deep public support and are defended by Iran's strongest forces, the Revolutionary Guard and a vast network of militias around the country.
But Mousavi's opposition movement has broken significant ground. It has forced Iran's most powerful figure, Supreme Leader Ayatollah Ali Khamenei, into the center of the escalating crisis and broken taboos about questioning his role as the final word on all critical matters.
"It's changing the way Iranians see the supreme leader and the system in general," said Meir Javedanfar, an Iranian affairs analyst. "That opens up they system up in ways it's never faced before."
Javedanfar believes two critical factors should be watched: whether the opposition movement can keep its show of strength on the streets for several more weeks and, more importantly, if it can bring in influential voices from Iran's Islamic clergy.
Shortly after the election, Mousavi appealed for the backing of clerics in the holy city of Qom, Iran's seat of Islamic learning and a critical political base for the theocracy. But received shows of support from several prominent liberal and dissident religious figures, including Grand Ayatollah Hossein Ali Montazeri, who said that "no sound mind" would accept the election results.
But Mousavi, who served as prime minister during the 1980s, has not captured widespread support among the Qom clerics. That doesn't mean, however, they are supporting Ahmadinejad, either.
Many have congratulated Khamenei for holding the election, but any mention of Ahmadinejad's victory was noticeably absent.
The wild card for Mousavi's movement is former President Hashemi Rafsanjani, who heads the Assembly of Experts - a cleric-run body that is empowered to choose or dismiss Iran's supreme leader. Khamenei is Ayatollah Ruhollah Khomeini's successor, and the assembly has never used its power to remove Iran's highest authority.
Rafsanjani was a fierce critic of Ahmadinejad during the election, but has not publicly backed Mousavi. It is not known whether Mousavi has actively courted Rafsanjani's support or if they have held talks.
But Iranian TV showed pictures of Faezeh Hashemi, Rafsanjani's daughter, speaking to hundreds of Mousavi supporters, carrying pictures of Khomeini.
Robin Niblett, director of the Royal Institute for International Affairs in London, said he does not believe Mousavi wants to topple Iran's theocracy, but his allegations of vote fraud could undermine the authority and respect of Khamenei.
"It is a split itself over this election and the broader grand strategy of the country," Niblett said. "I don't believe the protesters want to overthrow the system at this time - although their ire at Khamenei may yet increase."
Mousavi urged followers to wear black Thursday to the planned rally in mourning for the alleged election fraud and the lives lost in the protests. Seven demonstrators were shot Monday by pro-regime militia in the first confirmed deaths since the unrest erupted after the election.
Mousavi's call followed a rare public appeal to unite behind the Islamic state. Khamenei has normally remained aloof from direct involvement in political disputes, but the scope of crisis has pushed him into an unfamiliar role as mediator.
Mousavi's backers have now staged three straight days of major marches in Tehran, including hundreds of thousands of people Monday in a huge procession that recalled the protests of the Islamic Revolution.
An amateur video showed thousands marching Wednesday on an overpass in support of Mousavi's campaign.
BBC's Farsi-language news site reported Wednesday that protests also occurred in Shiraz, Tabriz and Mashad, though no serious violence was reported in those cities.
A crackdown on dissent continued, with more arrests of opposition figures reported, and the country's most powerful military force - the Revolutionary Guard - saying that Iranian Web sites and bloggers must remove materials that "create tension" or face legal action.
In one high-profile display of apparent support for the opposition, several Iranian soccer players wrapped their wrists with green tape - the color of Mousavi's campaign - during a World Cup qualifying match in South Korea that was televised in Iran.
In Paris, demonstrators held up banners saying "Freedom of Expression in Iran," and "Where is my vote?" near the Eiffel Tower. In Rome, about 300 people gathered to show solidarity with Mousavi.
The government has blocked certain Web sites, such as BBC Farsi, Facebook, Twitter and several pro-Mousavi sites that are vital conduits for Iranians to tell the world about protests and violence. Many other sites, including Gmail and Yahoo, were unusually slow and rarely connect.
Mousavi condemned the blocking of Web sites, saying the government did not tolerate the voice of the opposition.
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 disturbances. The Guard is a separate military with enormous domestic influence and control of Iran's most important defense programs. It is one of the establishment's key sources of power.
The statement alleged that dissident Web sites were backed by Canadian, U.S. and British interests, a frequent charge by hard-liners against the opposition.
"Legal action will be very strong and call on them to remove such materials," it said.
The U.S.-based International Campaign for Human Rights in Iran said several dozen noted figures associated with the reform movement have been arrested, among them politicians, intellectuals, activists and journalists.
Tehran-based analyst Saeed Leilaz, who is often quoted by Western media, was arrested Wednesday by plainclothes security officers who came to his home, said his wife, Sepehrnaz Panahi.
At least 10 Iranian journalists have been arrested since the election, Reporters Without Borders said.
The main electoral authority has said it was prepared to conduct a limited recount of ballots at sites where candidates claim irregularities. The re-count would be overseen by the Guardian Council, an unelected body of 12 clerics and Islamic law experts close to Khamenei.
Mousavi alleges the Guardian Council is not neutral and has already indicated it supports Ahmadinejad. He wants an independent investigation.
Murphy reported from Dubai, United Arab Emirates. Associated Press writer Shaya Tayefe Mohajer contributed to this report from Los Angeles.
Copyright 2013 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.