TEHRAN: Tens of thousands of supporters of Iran’s defeated presidential candidate Mir Hossein Mousavi demonstrated for a sixth straight day yesterday, keeping up the pressure on the government over the disputed vote.

The rally came as electoral watchdog, the Guardians Council, said it was investigating a total of 646 complaints of irregularities in the conduct of the poll from Mousavi and the other two defeated candidates.

It said it had invited the trio to list their grievances tomorrow, with a decision on Sunday about any possible recount in the June 12 election, which returned incumbent President Mahmoud Ahmadinejad to power.

Mousavi himself joined the crowds, most of whom were dressed in black as a mark of mourning for demonstrators killed in clashes during the protests which have been banned by the authorities. State radio has reported seven deaths since the protests started.

Facing their biggest crisis since the 1979 revolution against the shah, Iran’s rulers have gone on the offensive, arresting protesters and prominent reformists, tightening their grip on the media and lashing out at “meddling” by foreign foes, including the United States. Foreign journalists have been barred from attending all rallies or other events without express authority.

Besides the seven reported deaths, many more people have been wounded in the worst violence for at least a decade, with protests reported in provincial cities as well as Tehran.

Supreme leader Ayatollah Ali Khamenei said he would consider a partial recount after Ahmadinejad’s defeated challengers lodged formal complaints of vote-rigging. But Mousavi is insisting that the result of what he has described as a “shameful fraud” be annulled and a new vote called.

Warning they would crush any “velvet revolution,” the authorities have rounded up scores of people, including prominent reformists and even former government officials. In the latest sweep, police on Wednesday arrested Ebrahim Yazdi and Mohammad Tavasoli, veteran revolutionaries and leaders of Iran’s Liberation Movement, the Etemad Melli newspaper reported.

The Fars news agency meanwhile reported that a daughter and son of former President Ali Akbar Hashemi Rafsanjani, who has been a prominent supporter of Mousavi, have been barred from leaving the country over their alleged role in disturbances since the election. State television showed footage on Wednesday of Rafsanjani’s daughter Faezeh talking animatedly among protesters in Tehran. The former president’s son Mehdi Hashemi was also the target of verbal attacks by Ahmadinejad during the election campaign.

The Intelligence Ministry said yesterday it had uncovered a foreign-linked terrorist plot to plant bombs in mosques and other crowded places in Tehran during the election.

State broadcaster IRIB quoted a ministry statement as saying several terrorist groups had been discovered, adding they were linked to Iran’s foreign enemies. “Members of one of the uncovered networks were planning to plant bombs on election day at various crowded Tehran spots, including Ershad and Al-Nabi mosques,” the statement said, referring to two prominent mosques in the capital. It said this plot was uncovered on election day.