Timeline: Opposition protests in Iran

(Reuters) - Iranian opposition websites said security forces clashed with protesters as huge crowds marked the 31st anniversary of the Islamic revolution on Thursday.

Here is a summary of the main developments since Iran's June 12 presidential election:

June 12, 2009 - Mahmoud Ahmadinejad wins the presidential election, defeating challenger Mirhossein Mousavi. Thousands of people protesting against the election result clash with police. Mousavi calls result a "dangerous charade".

June 15 - Seven people are killed on the fringes of a huge march by Mousavi supporters in central Tehran, state media say. Pro-Mousavi demonstrations also take place in the cities of Rasht, Orumiyeh, Zahedan and Tabriz.

June 16 - The Guardian Council says it is ready to carry out a partial recount of ballots, but rules out annulling the poll. Thousands of pro-Mousavi demonstrators march in northern Tehran.

June 18 - Thousands of Mousavi's backers, wearing black, rally in Tehran to mourn those killed in the protests.

June 19 - Supreme Leader Ayatollah Ali Khamenei says protest leaders will be responsible for any bloodshed if rallies continue over the election, which he says Ahmadinejad won fairly by 11 million votes.

June 20 - State television says 450 people are detained during clashes in Tehran in which 10 people are killed, including Neda Agha-Soltan. Graphic footage of her death is seen around the world on the Internet.

June 23 - President Barack Obama says the U.S. is "appalled and outraged" by Iran's crackdown. Britain expels two Iranian diplomats after two of its own are expelled from Iran.

June 26 -- Hardline cleric Ahmad Khatami, a member of the Assembly of Experts, calls for execution of leading "rioters".

June 28 - Authorities detain several local British embassy staff for involvement in the unrest. Britain calls the arrests "harassment and intimidation" and demands their release.

July 17 - Clashes erupt between police and reformist protesters in Tehran for the first time in weeks after former President Akbar Hashemi Rafsanjani declares Iran in crisis.

July 30 - Clashes erupt after hundreds of Mousavi supporters gather to mourn Neda Agha-Soltan at Tehran's Behesht-e Zahra cemetery and police force Mousavi to leave.

Aug 1 - Trials begin of prominent moderates, charged with trying to overthrow the clerical establishment.

Aug 3 - Supreme Leader Khamenei formally approves Ahmadinejad's second term. He is sworn in two days later.

Aug 8 - A court charges a French woman, two Iranians working for the British and French embassies in Tehran and dozens of others with spying and aiding a Western plot to overthrow the system of clerical rule.

Aug 25 - A prosecutor demands "maximum punishment" for senior reformer Saeed Hajjarian, accused of acting against national security, in the fourth mass trial of moderates.

Nov 4 - Police clash with Mousavi supporters in Tehran at rally marking anniversary of 1979 U.S. embassy storming.

Nov 22 - A reformist former vice president, Mohammad Ali Abtahi, who was arrested after the election, has been sentenced to six years in jail, Iranian newspapers report. He is released on bail pending an appeal.

Dec 19 - Iran's most senior dissident cleric, Grand Ayatollah Hossein Ali Montazeri, dies, providing a fresh catalyst for renewed demonstrations. Iran later bans memorial services for him except in his birthplace and Qom.

Dec 27 - Opposition websites say eight people are killed in Tehran and other cities across Iran when thousands take to the streets. Police in Tehran say they are investigating the "suspicious" deaths. Among the dead was Mousavi's nephew.

Jan 28, 2010 - Iran executes two people who were among a group of 11 sentenced to death on charges including waging war against God and trying to overthrow the Islamic establishment, the ISNA news agency says.

Jan 30 - The trial begins of 16 opposition protesters charged over unrest. Five defendants are charged with the capital offence of "moharebeh" (waging war against God); rest are accused of public order and national security offences.

Feb 11 - Opposition websites say security forces clash with protesters and arrest dozens as huge crowds mark the 31st anniversary of the Islamic revolution.