Britain today condemned the arrest of nine employees of the British embassy in Tehran and demanded their immediate release.

An Iranian news agency reported this morning that the Iranian workers had been detained for involvement in the post-election unrest in the Islamic Republic.

The arrests follow a week of escalating rhetoric against Britain, which was accused by the Iranian foreign minister of flying in jet-loads of spies to disrupt Iran's presidential elections on July 12.

The escalation came as reports emerged of further violence in Tehran tonight, in which hundreds of demonstrators were said to have clashed with soldiers and members of the country's Revolutionary Guard. No word has yet emerged of casualty numbers.

David Miliband, the Foreign Secretary, denied that the UK mission had been involved in any post-election unrest and called for the release of the embassy staff.

“This is harassment and intimidation of a kind that is quite unacceptable,” Mr Miliband told reporters during a security conference on the Greek island of Corfu.

“We want to see (them) released unharmed.”

News of the arrests emerged from Fars, a semi-official news agency, which said: “Eight local employees at the British embassy who had a considerable role in recent unrest were taken into custody.” It did not say when the arrests occurred.

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

Mr Miliband said that about nine employees had been detained in total, but some had been released.

“We are still concerned about a number of them who to our knowledge have not been released ... The numbers are changing hour by hour,” he said.

“These are hard-working diplomatic staff and 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.”

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