The Global Sumud Flotilla said more than a dozen explosions were heard around the flotilla as it sailed off Greece late on Tuesday, with damage caused by "unidentified objects" dropped on deck.

"To ensure assistance to the Italian citizens on the 'Flotilla'... I spoke with the Prime Minister and authorised the immediate intervention of the Italian Navy's multi-purpose frigate Fasan, which was sailing north of Crete as part of Operation Safe Sea," Crosetto said in a statement posted by the ministry on X.

"The vessel is already en route to the area for possible rescue operations", he said.

Crosetto expressed "the strongest condemnation" of the "attack" on the flotilla using "drones by currently unidentified perpetrators".

Foreign Minister Antonio Tajani said he had asked Israel to ensure the safety of "Italian citizens, along with members of parliament and MEPs" among the pro-Palestinian activists.

The ministry had already informed Israel that "any operation entrusted to Israeli forces must be conducted in compliance with international law and the principle of absolute caution," the ministry said in a statement.

"Minister Tajani has asked the Italian Embassy in Tel Aviv to gather information and to reiterate its previous request to the Israeli government to guarantee the absolute protection of the personnel on board," it added.

The Global Sumud Flotilla set sail from Barcelona earlier this month with the aim of breaking the Israeli blockade of Gaza and delivering aid to the territory.

It currently numbers 51 vessels, most of which are off the Greek island of Crete.

Vessels waiting to join the flotilla had already been targeted in two suspected drone attacks in Tunisia. Swedish climate activist Greta Thunberg was among those who boarded in the North African nation.

Israel, which blocked two previous attempts by activists to reach Gaza by sea in June and July, said Monday it would not allow the flotilla to reach the embattled Palestinian territory.