British embassy worker Hossein Rassam is seen among others at the mass trial in Iran
Two Iranian employees of the British and French embassies and a French teacher have gone on trial in Tehran alongside Iranian opposition figures.
Hundreds were arrested during protests that erupted in the wake of the disputed 12 June presidential election.
Those on trial are accused of acting against Iran's national security by taking part in the protests and spying.
France called for the French teacher and embassy employee to be freed. The EU expressed its concern at the trial.
Last week more than 100 people appeared in court in Tehran on charges including conspiracy. Several leading reformers were among the detainees.
Opposition leaders say such proceedings are "show trials".
There were reports on Saturday that riot police dispersed a large crowd, including relatives of defendants, outside the court.
'Spying for foreigners'
This is the second group trial of those accused of taking part in the post-election unrest. Reformist lawmakers and journalists were among the group, all wearing grey prison clothes.
Hossein Rassam, the most senior Iranian employee at the British embassy, is accused of "spying for foreigners", Iranian state media quoted the judge as saying.
Mr Rassam was held after the protests with eight other embassy colleagues and later released on bail.
Prosecutors accuse him of monitoring the riots on the ground along with two UK diplomats who have since been expelled.
The prosecutors say he was asked to meet representatives of political groups, ethnic and religious minorities and student groups, and inform London about the riots, state media reported.
State media said Mr Rassam had apologised for "the clear violations he had committed".
In London, a spokeswoman for the Foreign Office called the trial "completely unacceptable".
"We deplore these trials and the so-called confessions of prisoners who have been denied their basic human rights," she said.
An Iranian employee of the French embassy, Nazak Ashfar, was also in the dock, state media said, as was French teacher Clotilde Reiss.
The 24-year-old was stopped on 1 July as she prepared to leave Tehran, having spent five months as a university teaching assistant.
She is accused of "collecting information and provoking rioters", and has been charged with acting against national security, Irna news agency said.
Hundreds were detained after violent protests that followed June's election
The agency said she had told the court that she had written a one-page report about the situation in Isfahan and given it to the French embassy's cultural section.
Ms Reiss told the court she regretted taking part in the protests.
"My motive to take part in the gatherings was a personal one. But I accept that it was a mistake and I should not have gone to these gatherings," she told the court, according to AFP.
The French foreign ministry said on Saturday that the allegations against her were "devoid of any foundation", and that those against Nazak Ashfar were "non-existent".
The Swedish presidency of the EU expressed concern at the trial, saying it considered it an act against the whole European Union.
Rights groups say that hundreds of people including reformist politicians, journalists, activists and lawyers have been detained in Iran since the election.
The poll saw President Mahmoud Ahmadinejad returned to power, but opposition leaders insist the election was rigged.
In last week's trials, some of those in the dock made public confessions, saying they had made up their complaints against the elections to provoke unrest.
However, Iran's Prosecutor General, Ghorban Ali Dori Najafabadi, has said that confessions will not be the sole basis for the prosecution of suspects.
"The judicial system will base its ruling on the suspects' files and the evidence presented at courts," he was quoted as saying on Thursday.
He denied that the confessions were extracted using illegal measures.