* World's largest Muslim body condemns un-Islamic act
* Anger grows after Boko Haram threatens to sell girls
By Sami Aboudi and Tom Heneghan
DUBAI, May 8 (Reuters) - Islamic scholars and human rights officials of the world's largest Muslim organisation on Thursday denounced the mass kidnapping of Nigerian schoolgirls by the militant group Boko Haram as "a gross misinterpretation of Islam".
The statements from a research institute and human rights committee of the Organisation of Islamic Cooperation (OIC) echoed denunciations of the radical Islamist group by religious leaders and officials in Nigeria and several Muslim countries.
Boko Haram says it wants to establish a "pure" Islamic state in Nigeria and its leader Abubakar Shekau declared in a video on Monday that "Allah has instructed me to sell ... on the market" the more than 200 girls abducted from their school on April 14.
That video appears to have prompted Islamic officials to speak out against Boko Haram's radical religious views.
"This crime and other crimes carried out by such extremist organisations negate all human principles and moral values and stand in contradiction to the clear teachings of the blessed Koran and the rightful examples set by the Prophet (Mohammad)," the OIC's International Islamic Fiqh Academy said.
"The secretariat of the academy, shocked by this ugly act, strongly demands the immediate release of these innocent girls without causing any harm to any of them," said a statement posted on the website of the academy in Jeddah, Saudi Arabia.
The OIC's human rights commission condemned "the barbaric act of abducting the innocent schoolgirls" and the "misguided claim of Boko Haram" that selling them as slaves was Islamic.
This was "a gross misrepresentation of Islam," it said.
SECURITY FORCES CRITICISED
Jama'atu Nasril Islam, Nigeria's national umbrella group of Muslim organisations, denounced the kidnapping as an "act of barbarism" on April 16, shortly after it became known.
It also criticised Nigeria's security forces for allowing the abduction despite a state of emergency in force in Borno state, where it occurred, and a "huge amount of resources earmarked for security operatives."
International attention has grown as public anger mounts in Nigeria over the failure of government forces to find the girls.
Foreign countries including the United States, Britain and France have offered in recent days to help search for them.
This week, Al-Azhar, the prestigious Cairo-based seat of Sunni learning, said in a statement the kidnapping "has nothing to do with the tolerant and noble teachings of Islam."
Egypt's Religious Affairs Minister Mohammed Makhtar Gomaa called it "a terrorist act."
Malala Yousafzai, the Pakistani schoolgirl shot in the head by the Taliban in 2012 for defending girls' education, told CNN on Wednesday the Nigerian girls were her sisters and their Boko Haram kidnappers "should learn Islam".
Boko Haram has led a five-year-old insurgency with the stated aim of reviving a medieval Islamic caliphate in modern Nigeria, whose 170 million people are split roughly evenly between Christians and Muslims.
Its violent attacks have become by far the biggest security threat to Africa's top oil producer and it has spread out to menace the neighbouring countries of Cameroon, Niger and Chad.
Nigerian President Goodluck Jonathan pledged on Thursday to find the abducted schoolgirls but admitted on national television this week that he had no idea where they were.