ISTANBUL, Sept 3 (Reuters) - Turkey said on Saturday that it would apply next week for an investigation by the International Court of Justice into the legality of Israel's naval blockade of the Palestinian enclave of Gaza.

Speaking to Turkish state-run television during a gathering of European foreign ministers in Poland, Foreign Minister Ahmet Davutoglu also reiterated Turkey's support for efforts to win recognition for a Palestinian state through the United Nations.

On Friday, Turkey expelled Israel's ambassador and froze military agreements with Israel after a U.N. report on the killing of nine Turks during an Israeli raid on a Gaza-bound ship a year ago failed to trigger an apology from the Jewish state.

Aside from demanding an apology, and compensation for families, Turkey also insists Israel ends the blockade of Palestinians living in Gaza.

Israel says the blockade is needed to stop arms reaching militants from the Islamist Hamas movement that controls Gaza.

The U.N. report concluded that the blockade was a legitimate security measure in order to prevent weapons entering Gaza by sea .

Davutoglu said Turkey did not accept that conclusion, noting that it contradicted the U.N. Human Rights Council's findings.

We will start the application process to International Court of Justice within the next week, for an investigation into what the Gaza blockade really is, Davutoglu told TRT news channel.

Turkey has also said it will pursue criminal cases against Israeli officials responsible for the killings of the nine Turks, one of whom was a U.S. citizen .

Turkey's Prime Minister Tayyip Erdogan, regarded as a hero in the Muslim world for championing the Palestinian cause, is expected to go to Egypt later this month for a visit that could deepen the rift with Israel.

There is speculation that Erdogan might go to Gaza through Egypt's Rafah border crossing to show solidarity with the Palestinians.

While both Turkey and Israel are allies of the West, the two have become estranged in recent years, largely because of the Palestinian issue.

A Turkish official said there were tentative plans for Erdogan to visit Egypt on Sept. 12, and, without specifying where, the official said Erdogan might go to another location during the trip.

Davutoglu warned Israel that the democratic forces unleashed by the Arab Spring would stoke animosity toward the Jewish state unless it changed its policies.

Israel has to make a choice, the Arab Spring will bring about a significant enmity against Israel if it fails to change its attitude regarding regional issues, Davutoglu told TRT news channel. (Reporting by Ece Toksabay; Writing by Simon Cameron-Moore; Editing by Rosalind Russell)