DUBAI, Oct 13 (Reuters) - Arab Sunni and Shi'ite Muslims have welcomed a rare religious edict from Iran's Supreme Leader Ali Khamenei against insulting revered Sunni figures that could help stem sectarian tensions in the Gulf region. The fatwa issued on Sept. 30 was not unusual in itself but the fact that Saudi Shi'ites publicly requested Khamenei's opinion and that it has been so widely welcomed by Sunnis and Shi'ites suggests Iran is winning the regional clout it craves.
"It is wrong in Islam to disparage symbols of our Sunni brothers as well as to accuse the wife of the Prophet and sully her honour. It is forbidden with respect to wives of the prophets and especially their master, our great prophet," the fatwa, published by Iran's Mehr news agency, said.
Khamenei was responding to Saudi Shi'ites from the Eastern Province who sought an ease in sectarian tensions following an incident in Kuwait where an outspoken Kuwaiti Shi'ite preacher insulted the Prophet Mohammad's wife Aisha, revered by Sunnis.
Kuwait last month stripped Yasser al-Habib of his citizenship and banned public gatherings for fear that the comments carried on his website could lead to clashes.
Underlying sectarian tensions in Muslim countries are often ignited by such issues concerning figures from early Islam.
The 2003 U.S. invasion of Iraq -- bringing to power Shi'ites who then drew close to non-Arab Shi'ite power Iran -- has created the atmosphere where these tensions flourish in a region traditionally dominated by Sunni elites.
Khamenei's intervention won widespread praise.
Kuwait's cabinet said in a statement on Monday it was an effort "to bury strife" and unite Muslim ranks.
Sheikh Ahmed El-Tayeb, the head of al-Azhar in Cairo, one of the most prominent seats of Sunni learning, said the fatwa came from "one of the most senior Muslim scholars" and Sheikh Yousef al-Qaradawi, a respected Egyptian cleric who lives in Qatar, praised the fatwa in his weekly appearance on Al Jazeera TV.
The fatwa suggests rising interest in Khamenei as a "source of emulation", or marja, for Shi'ites, said Amal Saad Ghorayeb, Lebanese author of a study on the Iranian-backed Lebanese Shi'ite group Hezbollah. Coming from the ultimate authority in Iran, it could help increase the Islamic Republic's reach in the region.
"This helps portray Iran as a non-sectarian power, as a religious authority on not just Shi'ite matters but as a protector of Islamic figures," she said.
"If Khamenei tries to engage in more ecumenical practices and forge a wider Islamic unity, that would definitely improve his chances of being embraced more openly by Shi'ites across the Arab world."
Ayatollah Ruhollah Khomeini, founder of Iran's Islamic revolution in 1979, instituted a new theory of Shi'ite Muslim statecraft -- known as velayat-e faqih -- where ultimate authority lies with an agreed-upon senior jurist in Islamic law.
The system was controversial, not least for conservative Arab governments oriented towards the West, since it merged political and religious power and created a possible alternative focus of allegiance for Shi'ite Muslims outside Iran.
The revolution emboldened Shi'ites in Saudi Arabia to rise in rebellion over their status in the Wahhabi state. Arab states funded Iraq's ruinous eight-year war with Iran in order to stave off the revolutionary threat to the regional political order.
Although Iran has in recent years returned to projecting its political power, extending its influence into Iraq and backing Palestinian Sunni Islamist group Hamas, Khamenei has not enjoyed the following beyond Iran of his predecessor Khomeini and is not regarded as one of the major clerics of Shi'ism.
There are no statistics, but most Gulf Arab Shi'ites are thought to favour Iraqi cleric Ali al-Sistani as their marja'. Many also followed Grand Ayatollah Sayyed Mohammed Hussein Fadlallah, a revered Lebanese cleric who died in July.
Sistani rarely offers opinions on political questions, and commentators had wondered whether Fadlallah's passing could create a vacuum that would further raise the stature of Iran and its Supreme Leader among the region's Shi'ites.
Jaafar al-Shayeb, a prominent Shi'ite figure in the Saudi town of Qatif, said the letter to Khamenei came from Saudis who follow not only the Iranian leader but other marjas as well.
"Most of the Shi'ites here are following Sistani. The fatwa directly applies to followers of Khamenei but for sure it will have an influence upon others," Shayeb said.
Iran's relations have stiffened with Gulf countries as international pressure mounts over Tehran's nuclear energy programme. Washington and its Gulf Arab allies fear Iran will become the Gulf's de facto policeman if it acquires nuclear weapons, encouraging Shi'ites in countries such as Saudi Arabia and Bahrain to push for more rights and power.
Shi'ites are a majority in Bahrain and number over two million in eastern Saudi Arabia, where most of the absolute monarchy's oil fields are located.
Mustafa Alani, a Dubai-based political analyst close to Gulf government circles, said Tehran had utilised a golden opportunity to grandstand to Sunni and Shi'ite audiences.
"Attacking Habib will cost you nothing, he's a maverick," he said, suggesting Tehran had connived with Saudi Shi'ites in the request for the fatwa. "This was a political statement, not only religious, since Khamenei is head of state."
Saudi Arabia's powerful Wahhabi religious establishment, a key motor driving anti-Shi'ite sentiment, reacted with dismay to the welcoming response to Khamenei's call for sectarian unity.
"We are not against Khamenei's fatwa at all, but we have learned not to be tricked or fall for the games of deceivers," one website almoslim.net said in an editorial comment. (Additional reporting by Diana Elias in Kuwait; editing by Ralph Boulton)