As polling stations in Iran have closed, both incumbent President Mahmoud Ahmadinejad and his main challenger Mirhossein Mousavi have claimed victory.

Voting was extended by four hours due to a high turnout, estimated at around 70 percent. Though there are no reliable exit polls, state news agency IRNA has declared President Ahmadinejad the winner. If none of the the four candidates secures an absolute majority outright, a run-off ballot will follow in a week's time. First results are expected on Saturday morning.

US President Barack Obama has expressed delight at the way the elections have been conducted. He particularly welcomed the brisk public debates held by the candidates during the campaign.

Former Prime Minister Mousavi, a reformist, focussed his criticism of President Ahmadinejad on his administration's foreign policy. He accused the president of isolating Iran in the international community. Mr Mousavi's support is particularly strong among urban people under 30 as well as intellectuals and writers.