Iranian opposition leaders are planning a united show of strength this week when they attend Friday prayers in Tehran led by influential cleric and former president Akbar Hashemi Rafsanjani.
Defeated presidential candidates Mir Hossein Mousavi and Mehdi Karroubi said they will join hundreds of other worshippers as the two-time ex-president delivers a sermon for the first time in more than two months.
"I will join the lines (of worshippers) on Friday as I feel obliged to respond to the call of companions on the path to protecting rights to a noble and free life," Mousavi said on his website Ghalamnews.
It will be Mousavi's first public appearance in weeks after his supporters held massive street protests against President Mahmoud Ahmadinejad's bitterly disputed re-election on June 12.
In a first government reaction to the planned gathering, Intelligence Minister Gholam Hossein Mohseni Ejeie warned "Iranian people must be careful so that the Friday prayers is not turned into a venue for unpleasant scenes."
"Hopefully we will not have a security question in Tehran in the coming days," he told Fars news agency on Thursday.
Mousavi, who was Ahmadinejad's closest rival in the election but lost heavily to the incumbent, has charged that the June vote was rigged and dismissed the next government as "illegitimate".
The anti-Ahmadinejad protests saw hundreds of thousands of demonstrators take to the streets of Tehran and other cities, triggering the worst crisis in the Islamic republic since the 1979 revolution.
The ensuing violence left at least 20 people dead, many scores wounded and hundreds arrested, according to official figures.
The protests shook the pillars of the Islamic republic and split the nation's clerical groups, while the crackdown by the authorities on demonstrators provoked worldwide outrage.
Iranian security forces backed by members of the volunteer Islamic Basij militia managed to stifle the protests, with all public gatherings banned, but demonstrators have defiantly taken to streets on several occasions.
Friday prayers this week have taken on a significance as Rafsanjani, a key Mousavi supporter who himself lost to Ahmadinejad in the 2005 presidential race, is reportedly expected to break his post-election silence.
He had come under attack from Ahmadinejad during a prime-time television debate in the run-up to the vote, with the hardline incumbent accusing Rafsanjani's family of corruption.
Mousavi's supporters are also reportedly planning to go to Friday prayers at Tehran university that are regularly attended by Islamic republic hardliners, setting the scene for a possible confrontation.
It is unclear whether the protesters will manage to gather in large numbers around the university on Enghelab (Revolution) street, scene of some of the biggest post-election protests.
Security forces brutally cracked down on protesters in the area on June 20 after Iran's supreme leader Ayatollah Ali Khamenei at Friday prayers urged an end to protests and warned that opposition leaders would be responsible for any bloodshed.
Iran's leading hardline newspaper Kayhan warned against "provocation" at the Friday prayers.
"We have even heard that some with a hezbollahi (Islamist) appearance intend to carry out these provocations. So worshippers should be careful not to be deceived and reject those who shout divisive slogans," it said.
There has been speculation in the Iranian press on how Rafsanjani will address the disputed election, with some saying he should express sympathy with families of the victims killed in the unrest.
Rafsanjani is yet to comment on election results although a key clerical institution, the Assembly of Experts, which he heads, hailed the mass turnout but made no mention of Ahmadinejad's victory in its post-vote statement.
Kayan said it expected Rafsanjani "to condemn rioters and their illegal and disturbing acts."
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