Fatou Bensouda, chief prosecutor of the Hague-based ICC, on Thursday said that there would be no investigation leading to a potential prosecution because the alleged crimes, including the killing of 10 activists by Israeli commandos, were not of "sufficient gravity".
"The information available provides a reasonable basis to believe that war crimes were committed on board the Comorian-registered vessel the Mavi Marmara during the interception of the flotilla," Bensouda said in a statement.
"However, after carefully assessing all relevant considerations, I have concluded that the potential case(s) likely arising from an investigation into this incident would not be of 'sufficient gravity' to justify further action by the ICC."
Nine Turkish nationals died when Israeli commandos staged a botched pre-dawn raid on a six-ship flotilla seeking to bust Israel's naval blockade of the Gaza Strip on May 31, 2010.
A tenth activist later died of his wounds, AFP reported.