MANAMA, Bahrain - In a stinging blow to Bahrain's leaders, a special commission that investigated the kingdom's unrest charged Wednesday that authorities used torture, excessive force and fast-track justice in crackdowns on the largest Arab Spring uprising in the Gulf.

The head of the panel, Mahmoud Cherif Bassiouni, also said there was no evidence of Iranian links to Bahrain's Shiite-led protests. That was a clear rebuke Gulf leaders, who accuse Tehran of playing a role in the 10-month-old showdown in the Western-allied kingdom.

The 500-page study -- authorized by Bahrain's Sunni rulers in a bid to ease tensions -- marks the most comprehensive document on security force actions during any of the revolts that have flared across the Arab world this year. It also displayed a stunning image of a powerful Arab monarch facing a harsh public reckoning, as King Hamad bin Isa Al Khalifa listened to a bullet-point summary of the report's conclusions.

Bassiouni's summary -- presented at a royal palace news conference attended by Bahrain's king and crown prince -- read like a checklist of complaints by rights groups since February: Middle-of-the-night raids to "create fear," purges from workplaces and universities, jail house abuses including electric shocks and beatings and destruction of Shiite mosques that "gave the impression of collective punishment."

At least 35 people have been killed in violence related to the uprising, including several members of the security forces.

It appeared unlikely that even the strong criticism would satisfy opposition forces, who accused the Sunni monarchy of using all methods at its disposal to avoid sharing power with the nation's Shiite majority. Just hours before the long-awaited report was released, security forces used tear gas and stun grenades in the latest of nearly daily clashes on the strategic island, home to the U.S. Navy's 5th Fleet.

Still, the inquest was seen as a bold step in a region of monarchs and sheiks who rarely acknowledge shortcomings or face uncomfortable criticism in public.

Bahrain's government promised "no immunity" for anyone suspected of abuses and said it would propose creating a permanent human rights commission.

"All those who have broken the law or ignored lawful orders and instructions will be held accountable," said a government statement, adding that the report notes that the "systematic practice of mistreatment" ended shortly after martial law was repealed on June 1.

Bahrain's Shiites comprise about 70 per cent of the island nation's 525,000 citizens. They have complained of widespread discrimination such as being blocked from top government or military posts. The monarchy has offered some concessions, but refused to bow to protest demands to surrender control of all top positions and main policies.

"A number of detainees were tortured ... which proved there was a deliberate practice by some," said Bassiouni, whose report covered the period between Feb. 14 and March 30.

The report also was highly critical of a special security court created under martial law that "overtook the national system of justice" and issued harsh sentences -- including life in prison and death row rulings -- that "denied most defendants elementary fair trial guarantees."

The document spotlighted abuses at the island's main hospital, the state-run Salmaniya Medical Center. The authorities saw its mostly Shiite staff as opposition sympathizers. Dozens of doctors and nurses who treated injured protesters were detained during crackdown. Many were sentenced to five to 15 year prison sentences. Their appeal will be heard in a civilian court.

"All reports indicated that there were protests, and indeed chaos, in the SMC," the report says, It adds, "The hospital generally continued to function normally" through the unrest.

Bahrain has abolished the security court. Bassiouni urged Bahrain to review all the security court verdicts and drop charges against all those accused of nonviolent acts such as joining or supporting the protests.

"You found real shortcomings from some government institutions," Bahrain's king told Bassiouni, an Egyptian-born professor of international criminal law and a former member of UN human rights panels.

But the king lashed back at finding that Iran did not influence the uprising, saying his government could not provide clear evidence but insisting Tehran's role was clear to "all who have eyes and ears."

He blamed Arabic-language outlets in Iran's state media of "inciting our population to engage in acts of violence, sabotage and insurrection. Iran's propaganda fueled the flames of sectarian strife -- an intolerable interference in our internal affairs."

Although Bahrain's bloodshed and chaos is small in comparison with the huge upheavals across the Arab world, the island's conflict resonates from Tehran to Washington.

Bahrain is a critical U.S. ally and Washington has taken a cautious line because of what's at stake: urging Bahrain's leaders to open more dialogue with the opposition, but avoiding too much public pressure.

Some U.S. lawmakers have shown signs of growing impatience with Bahrain's rulers. A $53 million arms deal with Bahrain is on hold until the upcoming report is examined.

For Gulf leaders, led by powerful Saudi Arabia, Bahrain is seen as a firewall to keep pro-reform protests from spreading further across the region. Gulf rulers have rallied behind the kingdom's embattled monarchy and sent in military reinforcements during the height of the crackdowns and Saudi-led units still remain.

Shiite-led protesters began occupying a square in the capital Manama in February -- just days after crowds in Cairo's Tahrir Square celebrated the downfall of Hosni Mubarak.

Weeks later, security forces stormed Manama's Pearl Square, tore down the landmark six-pronged monument at its center and imposed martial law. Hundreds of activists, political leaders and Shiite professionals such as lawyers, doctors, nurses and athletes were jailed and tried on anti-state crimes behind closed doors in a special security court that was set up during emergency rule.

On Tuesday, a group of Bahrain rights groups issued their own report on the unrest, accusing authorities of "systematic" abuses and "unceasing human rights violations."