Iran opposition leader Mir Hossein Mousavi said Saturday he was "ready for martyrdom," according to an ally, in leading protests that have shaken the Islamic Republic and brought warnings of bloodshed from Iran's Supreme Leader.
Mousavi also called for a national strike if he is arrested, a witness said. As darkness fell, rooftop cries of Allahu Akbar (God is greatest) sounded out across northern Tehran for nearly an hour, an echo of tactics used in the 1979 Islamic revolution against the Shah.
In an act fraught with symbolic significance, a suicide bomber blew himself up at the mausoleum of the father of Iran's Islamic revolution, Ayatollah Ruhollah Khomeini, while unrest continued across Tehran in defiance of a ban on demonstrations.
"A suicide bomber was killed at the northern wing of Imam Khomeini's shrine. Two people were injured," the semi-offical news agency Fars reported without giving further details.
Iran's deputy police chief for operations, Hossein Sajedinia said the bomber detonated his explosive vest and that the blast caused damage in the one section of the shrine.
The report could not be independently verified since foreign media are banned from reporting in Iran in the wake of the election controversy.
Mousavi, meanwhile, insisted the June presidential election should be annulled in a speech to a crowd of his supporters in Tehran on Saturday.
"These irritating measures (election rigging) were planned months ahead of the vote...considering all the violations...the election should be annulled," Mousavi said.
State television said rioters smashed windows of banks and burned buses. They also aired interviews with people critical of the demonstrations that have racked Iran since the announcement of the election results on June 13.
Earlier on Saturday one of the organizers of a mass rally in Tehran backed down after authorities threatened a harsh response as the Guardians Council, Iran's electoral watchdog, expressed readiness to "randomly" recount up to 10 percent of ballot boxes from last week's disputed presidential election.
The Guardians Council made its partial recount offer after meeting to study the 646 alleged poll violations registered by the three defeated candidates -- former parliament speaker Karroubi, former Prime Minister Mousavi and ex-Revolutionary Guards chief Mohsen Rezai.
Iran's security council had warned Mousavi he would be held responsible for consequences of "illegal" rallies, the semi-official ISNA news agency reported Saturday.
"Your national duty tells you to refrain from provoking illegal gatherings," council head Abbas Mohtaj, who is also deputy interior minister, said in a letter to Mousavi.
"Should you provoke and call for these illegal rallies you will be responsible for the consequences," he said.
Mohtaj also dismissed Mousavi's allegations about "the police vandalizing people's property."
In demanding an end to protests, Supreme Leader Ali Khamenei warned that otherwise there could be further bloodshed.
Siding with President Mahmoud Ahmadinejad in his first public appearance since the vote, Khamenei ruled out major fraud in the poll.
"The people have chosen whom they wanted," Khamenei said in a prayer sermon on Friday, referring to Ahmadinejad.
"I see some people more suitable for serving the country than others but the people made their choice," he said to cheers from tens of thousands of faithful, who included Ahmadinejad.
As darkness fell, Mousavi's supporters sent cries of Allahu Akbar (God is greatest) echoing across the rooftops in a reminder of the 1979 revolution.
Mousavi and his supporters have defied authorities and held several massive marches to protest against presidential poll results in Tehran following the announcement of Ahmadinejad's re-election.
On Wednesday he wrote an open letter to the council, demanding that vigilantes and unidentified plainclothes agents among the police are stopped from attacking demonstrators and destroying private property and cars.
Late on Friday, witnesses reported that many members of the hard-line Basij militia had deployed in Tehran streets, for the first time in full uniform and helmets, carrying clubs and some of them Kalashnikov rifles.
Amnesty International said on Friday it had information of at least 15 deaths.
Iran's capital has been rocked by daily demonstrations since the disputed re-election of President Ahmadinejad on June 12 drew claims from his leading rival, former premier Mousavi, of massive vote fraud.