Witnesses in Iran say police have clashed with up to 3,000 protesters near a mosque in north Tehran.
They say security forces fired tear gas to disperse the crowd, and some demonstrators fought back, chanting: "Where is my vote?"
Witnesses at the scene tell The Associated Press that some protesters claimed they suffered broken arms or legs in Sunday's clashes around the Ghoba Mosque.
They say some young demonstrators screamed at police and then attacked them after the officers allegedly beat an elderly woman.
The reports could not immediately be independently verified because of tight restrictions imposed on journalists in Iran.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
EDITOR'S NOTE: Iranian authorities have barred journalists for international news organizations from reporting on the streets and ordered them to stay in their offices. This report is based on the accounts of witnesses reached in Iran and official statements carried on Iranian media.
Iranian authorities have detained several local employees of the British Embassy in Tehran, a move that Britain's foreign secretary Sunday called "harassment and intimidation" and reflected a hardening of the regime's stance toward the West. The European Union condemned the arrests.
Iranian media said eight local embassy staff were detained for an alleged role in postelection protests, but gave no further details. British Foreign Secretary David Miliband said "about nine" employees were detained Saturday and that four had been released.
EU foreign ministers meeting in Corfu, Greece, issued a statement Sunday condemning the arrests and calling for the immediate release of all those still detained. The 27-nation bloc also denounced Iran's continuing restrictions on journalists.
"They make clear to the Iranian authorities that harassment or intimidation of foreign or Iranian staff working in embassies will be met with a strong and collective EU response," the statement said.
Opposition leader Mir Hossein Mousavi has alleged massive fraud in the June 12 presidential election and says he is the rightful winner, not President Mahmoud Ahmadinejad.
Iran has accused the West of stoking unrest, singling out Britain and the U.S. for alleged meddling and for expressing concern about the ferocity of the regime's crackdown on protesters. Last week, Iran expelled two British diplomats, and Britain responded in kind. Iran has also said it's considering downgrading diplomatic ties with Britain.
On Sunday, the semiofficial Fars news agency reported that the embassy staffers were detained for what was described as a "significant role" in postelection unrest.
The British Foreign Office says the embassy has a staff of more than 100, including at least 70 locally hired Iranians. Last week, Britain sent home 12 dependents of embassy staff because the protests had disrupted their lives.
Miliband, in Corfu for the EU meeting, said Britain lodged a protest with the Iranian authorities over the detentions. He described the step as "harassment and intimidation of a kind that is quite unacceptable."
"The idea that the British Embassy is somehow behind the demonstrations and protests that have been taking place in Tehran. ... is wholly without foundation," he said.
In London, a Foreign Office spokeswoman, speaking on customary condition of anonymity, said any further harassment of British Embassy employees would be met with "a strong and united EU response." She declined to comment on whether Britain was considering recalling its ambassador in protest or for consultations.
Iran's government has tried to discredit opposition supporters by alleging they have been directed by the West.
On Friday, a senior Iranian cleric, Ahmed Khatami, lashed out at Britain in a nationally televised sermon. "In this unrest, Britons have behaved very mischievously and it is fair to add the slogan of 'down with England' to the slogan of 'down with USA,'" he said.
Britain, a colonial power in the region with a long history in Iran, has been a prominent target. Britain and the U.S. were behind the 1953 coup that toppled Prime Minster Mohammad Mossadegh, who nationalized Iran's oil industry. Britain had almost complete control over Iran's oil industry for decades.
The British have also drawn fire because of the BBC's prominent role as a trusted broadcaster in Farsi inside Iran.
This is a reversal from the way the state and publicly funded BBC was perceived in the run-up to the Iranian Islamic Revolution. At the time, the BBC was widely listened to because it extensively covered anti-Shah demonstrations and activities of the Islamic Republic's founder, Ayatollah Ruhollah Khomeini, who was in exile in France.
Iran's leaders have countered Western condemnation with increasingly angry rhetoric. The confrontation appears to be dashing hopes for a new dialogue, as initially envisioned by President Barack Obama when he took office.
Obama wants to engage Iranian leaders in talks over the country's suspect nuclear program which the U.S. and other western countries worry is aimed at developing nuclear weapons. Iran defends its nuclear program as civilian in nature. On Sunday, EU foreign policy chief Javier Solana said the bloc would "like very much" to restart nuclear talks with Tehran despite the rising tensions.
Senior White House adviser David Axelrod played down Ahmadinejad's accusations against the U.S., saying Sunday they aren't credible and are meant for domestic consumption. "This is political theater," he said on ABC's "This Week."
Iran's rulers have unleashed club-wielding militiamen to crush street protests and arrested hundreds of journalists, students and activists.
On Sunday, Iran's supreme leader, Ayatollah Ali Khamenei called for national unity, appealing to both sides in the dispute, even though he has come down firmly on the side of Ahmadinejad.
"I admonish both sides not to stoke the emotions of the young or pit the people against each other," he said in comments carried on state TV. "Our people are made of one fabric."
Mousavi signaled he is not dropping his political challenge.
In a new statement, he insisted on a repeat of the election and rejected a partial recount being proposed by the government. However, Mousavi's challenge seemed largely aimed at maintaining some role as an opposition figure.
The latest statement by Mousavi, who has been increasingly isolated, appeared Sunday on Ghalamnews, a Web site run by supporters. Mousavi-related Web sites have frequently been blocked by the government, and one was shut down by hackers last week.
Iran's top electoral body, the 12-member Guardian Council, has proposed recounting 10 percent of the votes. On Friday, the council offered to bring in six more political figures to oversee a partial recount, presumably to give the effort greater legitimacy in the eyes of the challengers.
However, Mousavi reiterated his demand for nullification as "the most suitable solution to restore public confidence." He called for independent arbiters to settle the dispute.
Another defeated candidate, Mahdi Karroubi, also expressed doubt that a fair review is possible.
"How is it possible to answer controversies through counting some ballots?" he wrote in a letter to the Guardian Council, published Sunday in his newspaper, Etemad-e-Melli.
A third candidate, Mohsen Rezaei, said he would only send a representative to the council, for observation of a re-count, if the other two candidates did the same.
Laub reported from Cairo. Associated Press writers Shaya Tayefe Mohajer and William J. Kole in Cairo, Shawn Pogatchnik in London and Elena Becatoros in Corfu, Greece, contributed to this report.