Tehran, Iran ? Thousands of protesters defied Iran’s highest authority Saturday and marched on waiting security forces that fought back with baton charges, tear gas and water cannons as the crisis over disputed elections lurched into volatile new ground.

In a separate incident, a state-run television channel reported that a suicide bombing at the shrine of the Islamic Revolution leader Ayatollah Ruhollah Khomeini killed at least two people and wounded eight. The report could be not independently evaluated due to government restrictions on journalists.

If proven true, the reports could enrage conservatives and bring strains among backers of opposition leader Mir Hossein Mousavi. Another state channel broadcast images of broken glass but no other damage or casualties, and showed a witness saying three people had been wounded.

The extent of injuries in the street battles also was unclear. Some witnesses said dozens were hurt and gunfire was heard.

Some bloggers and Twitter users claimed that there had been numerous fatalities in Saturday’s unrest, reports that could not be immediately verified.

The clashes along one of Tehran’s main avenues — as described by witnesses — had far fewer demonstrators than recent mass rallies for Mousavi. But they marked another blow to authorities who sought to intimidate protesters with harsh warnings and lines of black-clad police three deep in places.

The rallies also left questions about Mousavi’s ability to hold together his protest movement, which claims that widespread fraud in June 12 elections robbed Mousavi of victory and kept hardline President Mahmoud Ahmadinejad in office.

Mousavi bewildered many followers by not directly replying to the ultimatum issued Friday by Iran’s most powerful figure, Supreme Leader Ayatollah Ali Khamenei. His stern order to Mousavi and others: Call off demonstrations or risk being held responsible for “bloodshed, violence and rioting.”