The White House on Monday said it "deeply regretted" the loss of life and injuries sustained in the clashes after Israel Navy troops stormed a convoy of international activists bringing aid to the Gaza Strip, leaving at least 10 people dead, Haaretz reported.
"The United States deeply regrets the loss of life and injuries sustained, and is currently working to understand the circumstances surrounding this tragedy," said White House spokesman William Burton.
United Nations Secretary-General Ban Ki-moon called for a full investigation and expressed shock at Israel's storming of the flotilla.
"It is vital that there is a full investigation to determine exactly how this bloodshed took place. I believe Israel must urgently provide a full explanation," he said at a press conference in the Ugandan capital of Kampala.
France became the first European nation to respond to the early morning's events. Foreign Minister Bernard Kouchner said he was "profoundly shocked".
Many of the activists aboard the protest ships were European nationals and analysts have predicted a harsh diplomatic response from the European Union and its member states.
Many of the activists aboard the protest ships were European nationals and analysts have predicted a harsh diplomatic response from the European Union and its member states.
The European Union demanded an inquiry and Germany said it was "shocked". The United Nations condemned violence against civilians in international waters.
Germany, one of Israel's most loyal allies, expressed shock at the deadly interception and questioned whether the action by Israeli commandos was proportionate.
Two members of the Bundestag lower house of parliament were among five Germans on board the ships, the foreign ministry said.
"The German government is shocked by events in the international waters by Gaza," government spokesman Ulrich Wilhelm told a regular news conference, adding the government was seeking further clarification about the incident.
"Every German government supports unconditionally Israel's right to self defense," said Wilhelm. But he added that Israeli actions should to correspond to what he described as the "basic principle" of proportionality.
"A first look does not speak in favor of this basic principle being adhered to," he said. Berlin would await further details before judging the incident, he added.
Italy also condemned the killing of civilians during Israel's storming of the aid flotilla as "very grave" and asked for an EU investigation to ascertain the facts.
"I deplore in the strongest terms the killing of civilians. This is certainly a grave act," said Foreign Minister Franco Frattini.
Referring to the European Commission, he said it was "indispensable that there be an inquest to ascertain the facts, which are still not clear."
He also said he had asked the Israeli ambassador for clarification and hoped that it would not hurt efforts on the part of Israel and Turkey to cooperate in the search for Middle East peace.