TEHRAN, (Reuters) – A hardline Iranian cleric on Friday called for the execution of “rioters”, in a sign of the authorities’ determination to stamp out opposition to the June 12 presidential election result.

Iran’s top legislative body, the Guardian Council, said it had found no major violations in the election, which it called the “healthiest” vote since the 1979 Islamic Revolution.

The council had already rejected a call for the annulment of the vote by moderate former Prime Minister Mirhossein Mousavi, who has led mass protests since he was declared a distant second in the election behind incumbent President Mahmoud Ahmadinejad.

“I want the judiciary to … punish leading rioters firmly and without showing any mercy to teach everyone a lesson,” Ahmad Khatami told worshippers at Tehran University.

Iranian state television said on Thursday eight Basij militiamen were killed by “rioters” during the protests. State media previously said 20 people were killed in the marches.

Iranian authorities have accused Mousavi of being responsible for the bloodshed, while the moderate former prime minister says the government is to blame.

Khatami, a member of the Assembly of Experts, said the judiciary should charge the leading “rioters” as being “mohareb” or one who wages war against God. “They should be punished ruthlessly and savagely,” he said. Under Iran’s Islamic law, punishment for people convicted as mohareb is execution.

Mousavi’s supporters plan to release thousands of balloons on Friday with the message: “Nada you will always remain in our hearts”, in memory of Nada Agha Soltan, the young woman killed last week who has become an icon of the demonstrations.

Khatami said Nada was killed by the rioters themselves for propaganda purposes. “By watching the film, any wise person can understand that rioters killed her,” he said.

Britain’s Times newspaper quoted Dr. Arash Hejazi, an Iranian who appeared on Internet videos helping Nada, as echoing opposition charges the 26-year-old music student was killed by a government militiaman. “She was just a person in the street who was against the injustice going on in her country, and for that she was murdered,” he said. Hejazi said that after the protest he left Iran for Britain, where he is resident, fearing arrest.

The authorities have used a combination of warnings, arrests and the threat of police action to drive large demonstrations off Tehran’s street since Saturday with small gatherings dispersed with tear gas and baton charges.

Russia, which along with China congratulated Ahmadinejad on his re-election earlier this month, said on Friday it was seriously concerned by the use of force in Iran.

“We naturally express our most serious concern about the use of force and the death of civilians,” Russian Foreign Minister Sergei Lavrov was quoted as saying on the sidelines of a meeting of Group of Eight foreign ministers in Italy.

G8 powers meeting in Trieste were due to issue a statement deploring the violence and calling on Iran to settle the crisis soon through democratic dialogue and peaceful means.

A G8 draft statement seen by Reuters called on the Iranian government to “guarantee that the will of the Iranian people is reflected in the electoral process”.

Russia was among countries at the G8 anxious not to slam the door on possible talks with Iran, the world’s fifth largest oil exporter, over its nuclear programme.

“I think there is unity here that it is for the Iranian people to choose their government but it is for the Iranian government to protect their people,” British Foreign Secretary David Miliband said after the foreign ministers’ meeting.

The 12-man Guardian Council’s statement leaves little scope for more legal challenges to the election result, short of an attack on the position of Supreme Leader Ayatollah Ali Khamenei, who has expressed strong support for Ahmadinejad.

“The Guardian Council has almost finished reviewing defeated candidates’ election complaints…the reviews showed that the election was the healthiest since the revolution … There were no major violations in the election,” said Abbasali Kadkhodai, spokesman of the council.

Former President Akbar Hashemi Rafsanjani, a Mousavi ally, chairs the Assembly of Experts which has the constitutional power to depose Khamenei. The assembly has never tried to do so and Rasfanjani is seen as unlikely to take such a radical step.

Mousavi said he was determined to keep challenging the election results despite pressure to stop. He called on his supporters to continue “legal” protests and said restrictions on the opposition could lead to more violence.