Iran's opposition vows to go on challenging poll

The unrest has exposed unprecedented rifts within Iran's clerical establishment, with Supreme Leader Ayatollah Ali Khamenei, who normally stays above the political fray, siding strongly with anti-Western President Mahmoud Ahmadinejad.

The turmoil has also dimmed prospects for President Barack Obama's outreach to Iran over its nuclear programme, with Tehran blaming Britain and the United States for fomenting violence.

Obama has ramped up his previously muted criticism, saying he was "appalled and outraged" by the post-election crackdown.

Khamenei has upheld the result of the June 12 presidential poll that returned Ahmadinejad and has warned opposition leaders they would be responsible for any bloodshed.

About 20 people have been killed in the demonstrations, but police and militia have flooded Tehran's streets since Saturday, quelling the majority of protests after the most widespread anti-government unrest since the 1979 Islamic revolution.

"My personal judgement is that this is a country deeply split and emotionalised," a Western diplomat in the region said. The protests had shown how dissatisfied some parts of society were with the way Iran was run -- to the chagrin of its leadership.

"I think they are deeply shocked," the diplomat said. The authorities had managed to impose outward stability, but had paid a heavy moral price, he added.

Riot police swiftly dispersed a group of about 200 demonstrators with teargas on Wednesday, but the protest was a far cry from marches last week that attracted tens of thousands.

Protest cries of Allahu Akbar (God is Greatest) were heard from Tehran rooftops again overnight, although they were much more short-lived than on previous evenings in the capital.