"Several foreigners are among those who were arrested on the day of Ashoura," Moslehi told state television, without specifying the nationality of the detainees.

"They were leading a psychological war against the system ... They entered Iran two days before Ashoura. Their cameras and equipment have been seized."

Trials 'soon'

Iran has frequently blamed foreign powers for the political turmoil it has suffered since its disputed presidential election in June.

in depth

  Video: Tehran warns opposition protesters
  Video: Deadly clashes rock Iran
  Timeline: Iran after the election

Opposition supporters took to the streets in the wake of the poll, which saw Mahmoud Ahmadinejad, the president, re-elected for a second term in a vote the opposition said was rigged.

At least eight people died during the most recent clashes, including a nephew of Mir Hossein Mousavi, the opposition leader who had most closely challenged Ahmadinejad in the June elections.

Tehran had said it would put on trial seven people arrested during the recent protesters, but there was no official media coverage and the trials, scheduled for Sunday, appeared not to have gone ahead.

Gholamhoseein Mohseni Ejei, Iran's prosecutor general, was quoted by semi official Fars news agency as saying, as saying that the trials would go head "soon".

"Individuals who were arrested during Ashoura events are currently being interrogated and their trial will soon be held," he was quoted by semi-official Fars news agency as saying on Monday.

Other reports suggested that two of the seven trials had gone ahead.

Diplomatic delay

In the aftermath of the violence, a delegation of European legislators who had been due to travel to Iran to meet human rights activists and Iranian politicians have postponed their visit.

The state-run IRNA news agency quoted Ramin Mehmanparast, an Iranian foreign ministry spokesman, as saying a new date for the visit will be reached "by mutual agreement".

The planned visit had been criticised by members of the US congress who said in a letter to Jerzy Buzek, the head of the European Parliament, that it came at an "inappropriate" time.

Both the EU and the US have has condemned Iran's crackdown on opponents of Ahmadinejad and called for the rights of protesters to be respected.

The EU has also supported sanctions against Iran over Tehran's nuclear programme and several European cities have been the scenes of demonstrations of solidarity with the opposition movement.

Separately, in Iran, a pro-reform website said that 88 Tehran University professors had appealed to Ayatollah Ali Khamenei, Iran's supreme leader, to halt violence against opposition protesters.

The letter to Khamenei called the violent crackdown by security forces a sign of weakness in the ruling system and urged Khamenei to order arrests for those behind it.

The letter was posted on the Greenroad website on Monday.