ISTANBUL - Normal ties between Turkey and Israel are "unthinkable" until Israel apologizes for the nine Turks killed when Israeli troops stormed a Gaza-bound aid flotilla, Turkish Prime Minister Recep Tayyip Erdogan said on Saturday.

Speaking just days before the submission of a UN report on the raid in May last year, Erdogan said Turkey would never forget the nine men and condemned the continuing blockade of Gaza as "illegal and inhuman".

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"Unless Israel officially apologizes for its unlawful action which is against international laws and humanitarian values, pays compensation for the families of those who lost their lives and lifts its embargo on Gaza, normalization of relations between the two countries is unthinkable," he said.

Israel says its blockade is justified to prevent arms smugglers ferrying weapons to Hamas, the Islamist group which runs Gaza.

Erdogan opened his speech to foreign ambassadors to the Palestinian territories in Istanbul by naming each of the men killed in the raid on the Mavi Marmara ferry.

"We have not forgotten, nor will we forget, the self-sacrifice of our brothers, their memories and the massacre they were subjected to," he said.

Turkey withdrew its ambassador to Israel after the incident in May 2010, suspended military cooperation, and closed its airspace to Israeli military aircraft.

Israel has agreed in principle to pay compensation, but says its marines acted in self-defense after an initial boarding party was attacked.

Prime Minister Binyamin Netanyahu has so far voiced only "regret" for the deaths, but Israeli officials say support for a stronger show of contrition is spreading in his government.

While some see an apology as taking responsibility, other officials have said Netanyahu had received legal advice that an apology would forestall Turkish bids to prosecute in international courts.