Britain called on Iranian authorities to immediately release a group of local employees of the British Embassy in Tehran who, according to the semi-official Fars news agency, are accused of involvement in post-election unrest.

Foreign Secretary David Miliband, seen here on Saturday, called the arrests of British Embassy employees 'harassment and intimidation.' (Reuters)

British Foreign Secretary David Miliband has called Saturday's arrests of eight or nine staff members "harassment and intimidation."

"The United Kingdom is deeply concerned at the arrests, and in some cases, continued detention of some of our hardworking locally engaged staff in Tehran," he said Sunday while attending a meeting of foreign ministers on the Greek island of Corfu.

"This is harassment and intimidation of a kind which is quite unacceptable. These are hardworking diplomatic staff," Miliband told reporters.

"The idea that the British Embassy is somehow behind the demonstrations and protests that have been taking place in Tehran in recent weeks is wholly without foundation."

Miliband said four of the Iranians detained had been released but added, "We are still concerned about a number of them who to our knowledge have not been released. The numbers are changing hour by hour."

The British Foreign Office said its Tehran embassy has a staff of more than 100, including at least 70 locally hired Iranians.

The detentions signalled a further toughening of Iran's dealings with the West, which has become increasingly vocal in its condemnation of a crackdown on opposition supporters.

Iran has accused Western powers — mainly Britain and the U.S. — of inciting the protests, sparked by allegations of a fraudulent vote count following the June 12 presidential election that returned President Mahmoud Ahmadinejad to power.

In recent days, the Iranian government has widened a clampdown on opposition supporters who allege the presidential election was rigged.

Britain expelled two Iranian diplomats Tuesday in retaliation for Iran's decision to order out two staff members from the British Embassy in Tehran.

On Sunday, Supreme Leader Ayatollah Ali Khamenei denounced what he called "interfering statements" by Western officials following the election.

He also urged both sides in the bitter dispute "not to stoke the emotions of the young or pit the people against each other."

First unrest since Wednesday

Several thousand protesters — some chanting, "Where is my vote?" — clashed with riot police in Tehran on Sunday at a rally that was planned to coincide with a memorial held each year for Ayatollah Mohammad Beheshti. He became a martyr in the Islamic Republic after he was killed in a major anti-regime bombing in 1981.

Witnesses said riot police used tear gas and clubs to break up a crowd of up to 3,000 protesters who had gathered near north Tehran's Ghoba Mosque in the country's first major post-election unrest in four days.

Some described scenes of brutality, telling The Associated Press that some protesters suffered broken bones and alleging that police beat an elderly woman, prompting a screaming match with young demonstrators who then fought back.

The reports could not be independently verified because of tight restrictions imposed on journalists in Iran.

With files from The Associated Press