Tehran, Iran ? Iranian police fired tear gas and beat protesters to disperse thousands chanting “Neda lives!” Thursday at a memorial for victims of post-election violence held at the gravesite of the woman whose death made her an icon of the pro-reform movement, witnesses said.

The new wave of unrest showed the opposition’s continuing ability to harness anger over the crackdown, and more protests could erupt around the inauguration next week of President Mahmoud Ahmadinejad, whose government has been virtually paralyzed by the crisis.

Thursday’s memorial gathering marked the end of the traditional 40-day mourning period for Neda Agha Soltan, a 27-year-old music student who was shot to death June 20. Her dying moments were filmed and circulated widely on the Internet, making her name a rallying cry for the opposition.

“Neda is alive! Ahmadinejad is dead!” chanted protesters, many holding up single red roses tied with green ribbons, the signature color of the opposition.

Plainclothes forces dispersed the crowd with tear gas and batons — and with chants of “Death to those who are against the supreme leader,” according to witnesses and state television.

The witnesses spoke on condition of anonymity because they feared reprisal. The government has banned media from covering some events, including Thursday’s memorial.

Demonstrations that drew thousands more later spread to other parts of the capital, Tehran, and more clashes with security forces erupted. Police fired tear gas, shots in the air and paintballs at hundreds of protesters on Vali Asr Street and other major avenues, witnesses said. Protesters set tires and trash cans ablaze in response. There was no word on casualties.

The opposition claims Ahmadinejad’s election victory was a fraud and his government has been virtually paralyzed by the 7-week-old crisis. The president has come under attack from both the opposition and his own supporters, who were angered by his appointment of a controversial first vice president he was later forced to sack.

The government says 30 people have been killed in the crackdown, though human rights groups say the true number is likely much higher. Hundreds were arrested in the sweeps, including young protesters, politicians and longtime critics of the government.

Soltan and at least 24 others killed in the crackdown are buried at Behesht-e Zahra, the vast cemetery on Tehran’s southern outskirts, according to rights groups tracking the dead.

The site holds great symbolic weight. Many of those killed during the 1979 Islamic revolution are buried there, and the revolution’s leader Ayatollah Ruhollah Khomeini has a gigantic mausoleum complex nearby. Those killed in Iran’s 1980-1988 war with Iraq are also buried in the cemetery, and families frequently visit the graves.

During the revolution, the deaths of protesters prompted similar marches after the 40-day mourning period, which were often answered by security forces attacking mourners in a cycle that helped fuel the street uprising.

Police barred opposition leader Mir Hossein Mousavi from joining the crowd around Soltan’s grave Thursday, witnesses said. Mousavi and his supporters claim he is the true winner of the election.