is on course to be re-elected as president of Iran with a resounding poll win, according to electoral commission figures. With 80% of the vote counted, the commission said Mr Ahmadinejad had 65% support. He has claimed victory in an election marked by high turnout. His main rival, reformist Mir Hossein Mousavi, also claimed victory and has complained of voting irregularities. A candidate must secure 50% in the first round to avoid a run-off vote. However, the Iranian election commission said Mr Mousavi's share of the vote was around 32%. The state news agency Irna has declared Mr Ahmadinejad the "definite winner". His campaign manager Mojtaba Samareh Hachemi was quoted by the Fars news agency as saying: "According to the votes counted so far, the distance between Ahmadinejad and his rivals is so great that any doubts cast on this victory will be treated as a joke by the public."

The president's supporters celebrated by taking to motorbikes on the streets of Tehran, chanting "God is Great", while there were reports that a rally for Mr Mousavi was broken up. Those backing Mr Mousavi are waiting to hear from their candidate, who was reported to have cancelled a news conference scheduled for Saturday morning. The BBC's Tehran correspondent, Jon Leyne, says Mr Mousavi's next move is extremely important, adding that the reaction of Iran's Supreme Leader Ayatollah Ali Khamenei will also be telling.

Mr Mousavi could dispute the expected result and may feel it could only be possible with massive vote-rigging. Earlier, he said there was a shortage of ballot papers and alleged that millions of people had been denied the right to vote. His election monitors were not allowed enough access to polling stations, he added, saying he would deal seriously with any fraud.

Rival claims

BBC Iranian affairs analyst Sadeq Saba says nobody expected the margin of Mr Ahmadinejad's apparent victory to be so big.

He says supporters of Mr Mousavi have expressed shock and disbelief.

Overall, he adds, a victory for Mr Ahmadinejad would mean no significant change in Iran's foreign and domestic policy.

However, this election brought hope to millions of people that they could change the direction of the country through the ballot box, and those people are going to be deeply disappointed, our correspondent says.

The hope for peaceful reform in Iran may die for a long time to come, he adds.

Shortly after polling ended, both Mr Ahmadinejad and Mr Mousavi had declared victory. But as the results began to come in, Iranian TV began putting out calls for calm. One opposition newspaper has been closed down and BBC websites appear to have been blocked by the Iranian authorities.

There was no evidence of major demonstrations or protests throughout Saturday morning, with our correspondent in Tehran saying the city appeared to have returned to the pattern of two months ago, before election campaigning brought thousands of people onto the streets.

Large turnout

There had been a surge of interest in Iran's presidential election, with unprecedented live television debates between the candidates and rallies attended by thousands.

There were long queues of voters at polling stations, with officials predicting an "unprecedented" turnout as they extended voting hours by several hours to accommodate the queues on Friday. Election officials said the turnout was possibly higher than 80%. Four candidates contested the election, with Mohsen Razai and Mehdi Karroubi only registering a small percentage of votes.

Police have increased security to try to head off trouble from supporters of the losing candidates and all gatherings have been banned until the official results have been published. A report by the AFP news agency said that a group of Mousavi supporters had been dispersed from outside his campaign office by baton-wielding police. US President Barack Obama said as the polling drew to a close that he was "excited" by the robust debate taking place in the country.

President Ahmadinejad draws support mainly from the urban poor and rural areas, while his rivals have support among the middle classes and the educated urban population.

Iran is ruled under a system known as Velayat-e Faqih, or "Rule by the Supreme Jurist", who is currently Ayatollah Ali Khamenei.

It was adopted by an overwhelming majority in 1979 following the Islamic revolution which overthrew the autocratic Western-backed Shah.

But the constitution also stipulates that the people are the source of power and the country holds phased presidential and parliamentary elections every four years. All candidates are vetted by the powerful conservative-controlled Guardian Council, which also has the power to veto legislation it deems inconsistent with revolutionary principles.