Meanwhile, EU foreign policy chief Catherine Ashton also called for a timely enquiry into the deadly attacks on Monday, and for an "immediate, sustained and unconditional opening" of the crossing for the flow of humanitarian aid, commercial goods and persons to and from Gaza.
United Nations Secretary-General Ban Ki-moon said he was "shocked by reports of killing of people in boats carrying supply to Gaza" in international waters, and called for full investigations into the incident.
Robert Serry, UN special coordinator for the Middle East peace process, and Filippo Grandi, commissioner-general of the UN Relief and Works Agency also said in a joint statement that they "wish to make clear that such tragedies are entirely avoidable if Israel heeds the repeated calls of the international community to end its counterproductive and unacceptable blockade imposed on the Gaza Strip."
The UN Security Council is expected to meet on Monday afternoon for an emergency session to discuss the Israel's attack.
Meanwhile, the Cairo-based Arab League (AL) called on the international community to move as quickly as possible to stop Israel's actions which it described as terrorism and causing unrest in the region. The pan-Arab body has decided to hold an emergency meeting Tuesday on the incident.
"The Arab League Council will study all the repercussions and developments and take a stance that maintains the rights of the Palestinians and the legitimate Palestinian cause," AL's Deputy Secretary-General Ahmed bin Helli said Monday.