"We strongly condemn this gruesome and barbaric killing as a violation of Islamic beliefs and of universally-accepted international norms mandating the protection of prisoners and journalists during conflicts," said the Council on American-Islamic Relations, the nation's largest Muslim civil rights and advocacy organization.
CAIR's remarks came days after the ISIS released a video showing one of its members beheading American journalist James Foley, who was abducted in Syria in November 2012.
"The Geneva Conventions, the Quran -- Islam's revealed text -- and the traditions (hadith) of the Prophet Muhammad all require that prisoners not be harmed in any way. There can be no excuse or justification for such criminal and bloodthirsty actions," CAIR said.
Islamic Society of North America condemned the vicious execution of Foley at the hands of the terrorist group ISIS, terming it as "un-Islamic behaviour".
"ISIS actions have never been representative nor in accordance to the mainstream teachings of Islam. This act of murder cannot be justified according to the faith practiced by over 1.6 billion people," said ISNA President Mohamed Magid.
The Muslim Public Affairs Council condemned the "barbaric execution" of Foley and urged all people of conscience to take a stand against extremism.
"A major obstacle preventing the true message of Islam worldwide is extremism. In this, we are not alone. Sadly, extremists contaminate all religions," reads the Declaration Against Extremism.
"Thus, with this document, together we passionately reaffirm our opposition to extremists of all stripes, particularly all Muslim extremists who betray Islam's true message. Furthermore, we pledge to collectively condemn and act to prevent extremism in all forms," MPAC said.
Organisation of Islamic Cooperation Secretary General Iyad Ameen Madani condemned what ISIS is committing against innocent Christian Iraqis in Mosul and Nineveh including forced deportation under the threat of execution; thus further tearing apart the social fabric of the Iraqi people.
Recently, Saudi Arabia's Grand Mufti Sheik Abdulaziz Al al-Sheik has described ISIS as "enemy number one of Islam".
ISIS is an al-Qaeda splinter group and it has seized hundreds of square miles in Iraq and Syria.
Al Qaeda has distanced itself from the group, chiding it for its lack of teamwork in its aggressive, brutal expansion.
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