Iranian security forces clashed (Reuters) with opposition supporters commemorating the death of dissident Grand Ayatollah Hossein Ali Montazeri, signaling escalating tension in Iran six months after the country's disputed presidential election.

The reformist website Jaras said many demonstrators were injured and arrests were made during clashes in the city of Isfahan, during a day of mourning for Montazeri, a fierce critic of Iranian President Mahmoud Ahmadinejad's regime. Reformist website Parlemannews said at least fifty opposition backers, including four journalists, were arrested in Isfahan. Jaras also reported clashes in Najafabad, the city where Montazeri was born.

The BBC reports that the confrontations are part of a build-up to a big series of demonstrations expected over the weekend. Authorities have not yet confirmed the unrest in Isfahan, but the country's police chief Esmail Ahmadi Moghaddam told the semi-official Fars news agency that protests would not be tolerated.  "We advise this movement to end their activities," he said. "Otherwise those who violate the order will be fiercely confronted, based on the law."

Analysis:

A Washington Post editorial says Ahmadinejad's decision to defy the Obama administration's year-end deadline on nuclear negotiations is politically risky, since internal popular support is "as weak as ever."

In the Guardian, Norman Dombey says nothing in published intelligence documents shows Iran is close to having nuclear weapons.

Background:

A CFR Backgrounder examines Iran's nuclear program.