An Iranian court on Saturday charged a French woman, two Iranians working for the British and French embassies in Tehran and dozens of others with spying and aiding a Western plot to overthrow the system of clerical rule.

Britain said the trial of its embassy employee was an "outrage".

"We deplore these trials and the so-called confessions of prisoners who have been denied their basic human rights," a British Foreign Office spokeswoman said.

It was the second mass trial in a week aimed at uprooting the moderate opposition and ending protests that erupted after the disputed June 12 presidential election.

At least 26 people have been killed and hundreds arrested in post-election violence. Moderates say the poll was rigged for President Mahmoud Ahmadinejad to win, but officials say it was the "healthiest" vote since the 1979 Islamic revolution.

The election and protests have plunged Iran into its biggest internal crisis in 30 years, exposing deep rifts within the ruling clerical establishment in Iran, the world's fifth biggest oil producer.

French citizen Clotilde Reiss was charged with "acting against national security by taking part in unrest ...collecting news and information and sending pictures of the unrest abroad", state news agency IRNA said.

Espionage and acting against national security are punishable by death under Iran's Islamic law.

Reiss confessed her "mistakes" and asked for clemency, IRNA said. Nazak Afshar, an Iranian working for the French embassy, was also charged with "providing information over the vote unrest to foreigners".

"We were not authorised by the embassy to go to rallies but we were told to shelter protesters if necessary," Afshar said.

The British embassy employee, Hossein Rassam, was charged with espionage and confessed to handing information about the unrest to Washington, IRNA said.

"The local staff were asked by their superiors at the British embassy to attend the riots," IRNA quoted Rassam as saying to the court. Rassam was released on $100,000 bail on July 19.

“Several British diplomats attended rallies ... The British ambassador and the charge d'affaires also went to a rally."

Riot police used force to break up a protest by relatives of the accused outside the courtroom.

"Relatives of the defendants and a large group of people gathered in front of the court building on Saturday. When they chanted 'Allahu Akbar' (God is greatest), the riot police attacked them to disperse the crowd," the reformist Mosharekat website said.

Reiss has been held in Tehran's Evin Prison since she was arrested at a Tehran airport on July 1 on charges of espionage as she tried to leave Iran after spending five months in the central city of Isfahan.

Television showed Reiss, wearing a black Islamic gown and a white-brown headscarf, sitting in the front row in the courtroom. It was not clear whether she had a translator when the indictment was read.

France has rejected the charge against Reiss as "baseless" and French President Nicolas Sarkozy has called for her immediate release. The French Foreign Ministry said on Saturday it had no comment on Reiss for now.

"I wrote a one-page report about the situation in Isfahan ... and handed it over to the French embassy's cultural section," IRNA quoted her as saying in court.

Western vote meddling

At a mass trial last Saturday more than 100 reformists, including a former vice-president and several other prominent figures, were charged with offences that included acting against national security by fomenting post-election unrest.

Leading moderates, including defeated candidates Mirhossein Mousavi and Mehdi Karoubi, have defied Supreme Leader Ayatollah Ali Khamenei, who has formally endorsed Ahmadinejad.

They say the new government Ahmadinejad is to appoint will be illegitimate. Ahmadinejad has two weeks