BRUSSELS: A survey of defectors from the Islamic State group has found that many quit the organization because they decided it was too brutal or corrupt, or because it made war too frequently against other Sunni Muslims.

The survey, issued Monday by a London-based think tank, relied on the public statements of 58 people known to have left IS since last year.

Peter Neumann, the report's author, said its findings shatter the image of unity and determination that IS seeks to portray.

The survey found common narratives among defectors, including disappointment that life under IS is so harsh, that the group is corrupt and un-Islamic, and that it commits atrocities against other Sunni Muslims.

Neumann said the defectors' statements, if given wide circulation, could deter future recruits from joining Islamic State.