RIYADH, May 31 (Xinhua) -- The Organization of the Islamic Conference (OIC) strongly condemned an Israeli attack against an international aid fleet Gaza Freedom Flotilla, that has killed 20 activists. "This crime is a serious escalation and a flagrant violation of the international law and human values," OIC Secretary-General Ekmeleddin Ihsanoglu said in a statement. The chief of the pan-Islamic body also held Israel responsible for the safety of the activists and offered condolences to the families of the victims. Ihsanoglu also reiterated a call for ending the blockade imposed by Israel on the Gaza Strip for over four years. The statement said Ihsanoglu called upon the Arab and Islamic group in the United Nations to call urgent meetings at the UN Security Council and Human Rights Council to examine "this heinous crime." The secretary-general of the Jeddah-based body also said he would hold contacts with international sides to push for an investigation into the Israeli attack and "punish the Israeli officials over the crimes they commit against humanity."