TEHRAN - Iran's supreme leader Ayatollah Ali Khamenei on Monday formally endorsed hardliner Mahmoud Ahmadinejad as president for a new four-year term amid intense political turmoil in the Islamic republic.

But in a sign of the escalating feud between rival factions over Ahmadinejad's hotly disputed re-election, key opposition leaders were absent from the ceremony, state television said.

"Iranian people have voted in favour of a fight against arrogance, to confront destitution and spread justice," Arabic-language Al-Alam television quoted Khamenei as saying after confirming Ahmadinejad in office.

Ahmadinejad, 52, dressed in a grey suit, accepted the decree from Khamenei as he bowed before the all-powerful leader and kissed his shoulder.

Among those who did not attend were Ahmadinejad's defeated rivals Mir Hossein Mousavi and Mehdi Karroubi, along with powerful cleric Akbar Hashemi Rafsanjani and former reformist president Mohammad Khatami, it said.

However, Mohsen Rezai, the former head of the elite Revolutionary Guards who was Ahmadinejad's only conservative rival in the June 12 vote, was at the ceremony.

The election set off the worst crisis in Iran since the 1979 Islamic revolution, with deadly street protests, a raft of political trials and increasing divisions among the ruling elite.

Ahmadinejad, who is to be sworn in before parliament on Wednesday, has also come under fire from his own hardline camp, which has questioned his loyalty to Khamenei.

His landslide victory was met with a vast outpouring of public anger and opposition complaints the vote was rigged. At least 30 people were killed and several thousand protesters rounded up, including reform figures and journalists.

Ahmadinejad's re-election has also created a rift among the clergy, with several senior clerics siding with the opposition and condemning the post-election violence and the regime's treatment of its critics.

The authorities hit back with a heavy-handed crackdown on protesters, whom they accuse of seeking to overthrow the regime.

On Saturday, around 100 people were put on trial in a revolutionary court, a move slammed by the opposition which accused the authorities of torture but welcomed by hardliners who in turn accused Mousavi and Khatami of treason.

Another 10 people went on trial on Sunday.

Despite the protests, Khamenei has given strong backing to Ahmadinejad and dismissed the vote-rigging allegations, accusing Western governments, Britain in particular, of instigating unrest.

Relations with the West worsened during Ahmadinejad's first term over his frequent verbal attacks on Israel and his uncompromising stance on Tehran's nuclear drive, which world powers fear is a cover for weapons development.

Although key policy issues are decided by Khamenei, critics point the finger of blame at Ahmadinejad for three sets of UN Security Council sanctions over Iran's refusal to suspend uranium enrichment.

Opponents also accuse Ahmadinejad, who enjoyed windfall oil revenues in his first term, of mismanaging the economy, stoking inflation, wasting resources and manipulating statistics to cover his failures.

Ahmadinejad crossed swords with Khamenei after he appointed a controversial aide as his first vice president and took his time in dismissing him despite the orders of the man who has led the country for 20 years.

Ahmadinejad denies any rift with Khamenei, characterising his relationship with the supreme leader as one of "father and son."

Iran's crackdown on protesters drew international condemnation, including from arch-foe the United States.

After three decades of severed diplomatic ties, Washington this year made overtures to Tehran, offering talks over their long-standing disputes, including the nuclear issue.

Iran has yet to respond but has ruled out negotiations on the nuclear programme, insisting it is for solely peaceful ends.

Should Ahmadinejad stick to his guns on the nuclear programme, his second term is likely to be characterised by greater tension with the West, which has warned of tougher sanctions.

Iran's stance towards staunch US ally Israel is also likely to harden further. Israel, the Middle East's sole if undeclared nuclear armed state, has not ruled out military action to curb Tehran's atomic ambitions.