DUBAI, UNITED ARAB EMIRATES — Thousands of Iranians disputing the reelection of President Mahmoud Ahmadinejad marched at an unauthorized rally Sunday, defying truncheon-wielding security forces and dire threats by Iranian leaders.
Meanwhile, European leaders' hackles were raised by the arrest a day earlier of eight British Embassy staffers in Tehran, a move that has sharpened Iran's confrontation with the West over the disputed election and its violent aftermath. Several of the staffers, all Iranian nationals, were quickly released.
Supporters of Ahmadinejad's opponent, Mir-Hossein Mousavi, gathered at a mosque in northeast Tehran during an annual commemoration for 72 Iranian politicians killed in a bombing 28 years ago.
Videos on YouTube purported to show demonstrators with hands in the air in front of the Ghoba mosque, chanting boisterously in support of Mousavi.
According to a witness who has previously provided accurate information to The Times, numerous opposition figures attended the rally, including presidential candidate Mehdi Karroubi; Mousavi's wife, Zahra Rahnavard; and both the daughter and wife of Ayatollah Ali Akbar Hashemi Rafsanjani, a Mousavi supporter.
The witness said pro-government Basiji militiamen and plainclothes security officials on motorcycles surrounded the rally and that Mousavi himself addressed the gathering by cellphone, which was attached to a megaphone, but the witness could not hear what he said.
Protesters flashed victory signs as they filled the mosque and surrounding side streets. A female protester, covered completely by a black chador, taunted some of the police.
"Who are you?" she demanded, according to the witness. "Are you Muslims?"
Dumbfounded security officials stood and watched, the witness said.
Iran accused the local British Embassy staff members of "playing major parts" in the recent unrest over the election, which many Iranians and independent experts consider fraudulent, according to a report by Fars, a pro-Ahmadinejad news agency.
All eight embassy employees arrested were members of the mission's political section, a source said. Some were released after preliminary investigations, but some will remain in custody, the official Islamic Republic News Agency reported.
"The British Embassy played a crucial role in the recent unrest both through its local staff and via media," the news agency quoted the minister of intelligence and security, Gholamhossein Mohseni-Ejei, as saying Sunday.
"We have photos and videos of certain local employees of the British Embassy who collected news about the protests."
He accused the embassy of fueling the unrest by dispatching staff to rallies and spreading anti-government propaganda.
Foreign ministers of European states, gathered for a European Union conference in Greece, quickly condemned the arrests. Although the U.S. has not had diplomatic relations with Iran since shortly after the 1979 Islamic Revolution, France, Italy, Germany and Britain maintain robust diplomatic missions in Tehran.
"Harassment or intimidation of foreign or Iranian staff working in embassies will be met with a strong and collective EU response," said a statement issued by the foreign ministers.
Authorities with a search warrant detained at least one of the embassy staffers at his home Saturday morning. He was brought back to his apartment later in the evening, and authorities seized computers and documents.
British Foreign Secretary David Miliband condemned the arrest and continued detention of "hardworking" embassy staff.
"This is harassment and intimidation of a kind that is quite unacceptable," he said in an interview on BBC. "We want to see [them] released unharmed."
Britain expelled two Iranian diplomats from London last week after Tehran booted two British diplomats. Iranian authorities also ordered a BBC correspondent out of Tehran and arrested a British-Greek journalist.
In addition, Iranian authorities have targeted local United Nations staffers.
Supreme leader Ayatollah Ali Khamenei appealed for unity in comments broadcast Sunday on state television. "I urge both sides not to provoke the sentiments of the youth and refrain from pitting people against each other," he said in an address to judiciary officials. "This united nation should not be divided, and groups should not be provoked to act against each other. There are legal ways for resolving issues."
Special correspondents in Tehran contributed to this report.