Istanbul (AFP) - A summit in Istanbul of Muslim heads of state on Friday called for the creation of an international peacekeeping force to protect the Palestinians, as host Turkish President Recep Tayyip Erdogan accused Israel of "brutality" comparable to the Nazis.

The 57-member Organisation of Islamic Cooperation (OIC) -- seeking to bridge severe differences within the Muslim world -- said in a final communique that Israel had carried out the "wilful murder" of some 60 Palestinians on the Gaza border Monday.

It called "for the international protection of the Palestinian population, including through dispatching of international protection force".

Erdogan said the sending of such an "international peacekeeping force" was essential to help the Palestinians and stop the international community being a "spectator to massacres".

He compared such a force to the UN forces sent to deal with the aftermath of the Balkan wars in Bosnia and Kosovo.

The statement also angrily lashed out at the United States, saying that Washington was complicit in the "crimes" of Israel and "emboldened" its government by moving its embassy from Tel Aviv to Jerusalem.

- 'No difference with Nazis' -

The summit had been called at a few days notice by Erdogan, who had earlier addressed thousands at an open air rally in Istanbul to express solidarity with the Palestinians.

Speaking at the opening of the summit, Erdogan compared Israel's actions against the Palestinians in Gaza to the Nazi persecution of the Jews in the Holocaust during World War II.

"There is no difference between the atrocity faced by the Jewish people in Europe 75 years ago and the brutality that our Gaza brothers are subjected to," he said, accusing Israel of using methods "similar to the Nazis".

Around six million Jews were killed by the Nazis during World War II in the Holocaust.

Addressing the earlier rally, Prime Minister Binali Yildirim used similar language, saying Israel was "imitating Hitler and Mussolini" by occupying Palestinian territory and disregarding international law.

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Palestinian prime minister Rami Hamdallah -- stepping in for president Mahmud Abbas who this week had surgery on his ear -- told the rally that the US was "trying to provoke a religious conflict in the region" by moving its embassy to Jerusalem.

- 'Test for Islamic world' -

Erdogan complained that Muslims had too often given a "shy and cowardly" image to their foes and failed to sort out internal disagreements.

Describing the issue of Jerusalem as a "test", he said: "If we need to speak clearly, the Islamic world failed in the Jerusalem test."

This is the second emergency OIC meeting Erdogan has hosted in the space of half a year after the December 2017 summit, also in Istanbul, that denounced US President Donald Trump's decision to recognise Jerusalem as the capital of Israel.

Disputes between the OIC's key players -- notably between Sunni kingpin Saudi Arabia and Shiite Iran -- always complicate the adoption of any measures going beyond harsh rhetoric.

Riyadh -- which appears to have softened its stance on Israel as the influence of powerful Crown Prince Mohammed bin Salman has grown -- and its allies fear alienating the United States with tough measures against Tel Aviv.

Saudi Arabia's chief foreign policy preoccupation, shared with Israel, is ensuring US backing to contain Iran which both Riyadh and the Jewish state see as the main threat to regional peace.

In his speech, Iranian President Hassan Rouhani pointedly criticised "the silence of certain countries" without which "the Zionists would have never attempted such a brutality"

Both Cairo and Riyadh are wary of Turkey's support for the Muslim Brotherhood and Hamas, as well as its close alliance with Qatar which is currently under a Saudi-led blockade. the Egyptian and Saudi foreign ministers came but not the heads of state.

- 'Called to account' -

Erdogan has long craved a role as a Muslim leader within the entire Islamic world, rarely holding back with tirades against Israel even though Ankara has diplomatic relations with the Jewish state.

Tensions with Israel and hosting such a meeting also does Erdogan no harm with his core supporters as Turkey heads to presidential and parliamentary polls on June 24.

And he has emerged as one of the most outspoken critics of Israel after Monday's bloodshed, earlier this week even accusing the Jewish state of genocide.

He called for an international investigation into the "crimes" Israel has committed. "It will be called to account sooner or later," he said.