TIMELINE: Iranian election and aftermath

(Reuters) - Here is a summary of the main developments since Iran's June 12 presidential election, which took place against a background of tension with the West over Tehran's nuclear program.

June 13 - Hardline incumbent Mahmoud Ahmadinejad officially wins presidential election with nearly 63 percent of the vote compared with 34 percent for reformist challenger Mirhossein Mousavi, authorities say. Thousands of protesters clash with police. Mousavi calls result a "dangerous charade."

June 14 - Mousavi says he has formally asked Iran's Guardian Council to annul the election.

June 15 - Seven people are killed during a huge march by Mousavi supporters in central Tehran, state media says. There are also pro-Mousavi demonstrations in the cities of Rasht, Orumiyeh, Zahedan and Tabriz.

June 16 - Thousands of pro-Mousavi demonstrators march in northern Tehran. Ahmadinejad's supporters mobilize thousands of demonstrators in central Tehran.

-- Authorities ban foreign journalists from leaving their offices to cover street protests.

June 17 - Thousands march in central Tehran.

-- Ahmadinejad defends the legitimacy of the vote, telling a cabinet meeting it has "posed a great challenge to the West's democracy," Mehr news agency reports.

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

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

June 20 -- Riot police are deployed in force, firing teargas and using batons and water cannon to disperse groups of several hundred Iranians who had gathered across Tehran.

-- A suicide bomber blows himself up near the shrine of Iran's revolutionary founder Ayatollah Ruhollah Khomeini in Tehran, Iran's semi-official Mehr news agency reports.

-- State television says more than 450 people are detained during clashes in Tehran in which at least 10 people are killed including Neda Agha-Soltan who, according to her fiance, had been caught up accidentally in the protests. Graphic footage of the woman's death is seen around the world on the Internet.

June 21 -- Mousavi urges supporters to continue protests.

-- Ahmadinejad accuses the United States and Britain of interfering in Iran's affairs.

June 22 -- Hardline Revolutionary Guards issue a statement saying they will "firmly confront in a revolutionary way rioters and those who violate the law." Police break up a protest in Tehran hours after the Guards issued their statement.

June 23 - Guardian Council again rules out annulment of the poll, saying there have been no major polling irregularities.

-- Riot police and Basij militia on Tehran's main squares ward off mass protests.

-- U.S. President Barack Obama says the United States is "appalled and outraged" by Iran's crackdown.

-- Britain expels two Iranian diplomats after two of its diplomats had been expelled from Iran.

June 24 - Iran pursues a security crackdown to suppress any more unrest.

June 25 - Ahmadinejad accuses Obama of behaving like his predecessor (former president George W. Bush) toward Iran and says there is not much point in talking to Washington unless the U.S. president apologizes.

-- Seventy professors are detained after meeting Mousavi, his website says.

-- Mousavi says he is determined to keep challenging the election results despite pressure to stop his website reports.

-- State television says eight Basij militiamen were killed by "rioters" during the protests. State media previously had said 20 people were killed in the marches.

June 26 - The Guardian Council says it has found no major violations in the election, which it described as the "healthiest" since 1979.

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

-- The Group of Eight foreign ministers, meeting in Italy, say in a statement they deplored the post-election violence and it should be settled soon through democratic dialogue and peaceful means on the basis of the rule of law.

-- Russia says it is seriously concerned by the use of force in Iran.