KUWAIT, May 27 (Reuters) - Kuwait's emir, speaking days after an attack claimed by Islamic state killed 21 Shi'ites in neighbouring Saudi Arabia, said on Wednesday sectarian strife was the most serious threat facing Muslims and called for immediate action to tackle it.

Speaking at the opening session of a meeting of foreign ministers of the Organisation of the Islamic Cooperation (OIC), Sheikh Sabah al-Ahmed al-Sabah said Muslim countries must work together to confront terrorism. His remarks were echoed by Saudi Arabia's foreign minister.

"We must take a serious stand on the sectarian malady that has been shaking the structure of our nation and fragments it," the emir told foreign ministers and representatives from the 57-member OIC at its annual meeting.

"This fanaticism is the most dangerous to the existence of our nation ... We are all losers in this conflict, and the winner is the one who wants to inflame this destructive strife for their own objectives ..."

The emir did not mention the suicide bombing on Friday that killed 21 worshippers at a mosque in al-Qadeeh village, but commentators in Saudi Arabia dicsussing the attack have decried what some see as the kingdom's failure to curb sectarianism at home. ID:nL5N0YG1C8

The schism between Sunnis and Shi'ites dates from shortly after the dawn of Islam 14 centuries ago. In modern times, this often translated into rivalry between the Wahhabi fundamentalism of Sunni Saudi Arabia and the Shi'ite theocracy of Iran.

The overthrow of Saddam's Sunni minority rule by the U.S.-led invasion in 2003 and its replacement by a Shi'ite Islamist government under the influence of Iran has rekindled sectarian sensitivities.

Islamic State openly acknowledges it is trying to stir sectarian confrontation as a way of hastening the overthrow of the ruling Al Saud, and has called on young Saudi Sunnis in the kingdom to attack targets in the kingdom including Shi'ites.

Sunni powerhouse Saudi and Shi'ite power Iran are locked in a regional tussle for influence in the Middle East, where civil strife has claimed hundreds of thousands of lives mainly in Syria, Iraq and Yemen.

Saudi Foreign Minister Adel al-Jubeir echoed Sheikh Sabah's call.

"We are all eager to confront the threats that face the Islamic nation, foremost among them the phenomenon of terrorism, violence, extremism and sectarianism, which have wrought deep damage in the Islamic nation," Jubeir he said.

(Reporting by Ahmed Hagagy an Noah Browning in Dubai, writing by Sami Aboudi, Editing by William Maclean and Ralph Boulton) ((Sami.Aboudi@thomsonreuters.com; +97143918301;))

Keywords: OIC KUWAIT/SECTARIANISM