Italy’s defence minister has condemned what he said was an overnight drone attack by unidentified perpetrators on a flotilla trying to breach Israel’s naval blockade of Gaza to deliver aid.

Guido Crosetto also said he had ordered an Italian Navy frigate to head towards the 52 boats in the Global Sumud Flotilla (GSF), which are mostly off the coast of Crete, to assist Italian citizens on board.

The GSF said several boats reported explosions and unidentified objects being dropped, as well as drones overhead and communications jamming. It accused Israel of a “dangerous escalation”.

Israel’s government has not commented. But it has previously said it will not let the flotilla reach its destination.

The overnight incident happened about 50km (27 nautical miles) south of Crete.

Unverified CCTV video footage released by the GSF showed a man on board a yacht jumping onto the deck following what appeared to be an explosion nearby. An explosion was also visible in a second video that the GSF said was filmed from the vessel Spectre.

Passengers on the boats said they requested assistance from the Greek coastguard.

A coastguard source told Greece’s AMNA news agency that a Portuguese vessel from the European Union’s border agency, Frontex, was dispatched to the area but that it found no evidence of material damage to the boats.

Swedish climate change campaigner Greta Thunberg, who is among the prominent pro-Palestinian activists taking part in the flotilla, called the incident a “scare tactic”.

On Monday, the Israeli foreign ministry alleged that the flotilla was “organised by Hamas”, and called on its boats to unload their aid supplies at the port of Ashkelon for transfer to Gaza.

“Israel will not allow vessels to enter an active combat zone and will not allow the breach of a lawful naval blockade,” it warned.

The GSF has said its goal is to “break the illegal siege on Gaza by sea, open a humanitarian corridor, and end the ongoing genocide of the Palestinian people”.

Two weeks ago, it reported that two vessels were targeted in separate drone attacks while anchored off Tunisia. Tunisian authorities said they were investigating the claims.

In June, Thunberg was one of 12 people on board a Gaza-bound aid ship, the Madleen, that was intercepted by Israeli forces about 185km west of Gaza.

Another vessel carrying 21 people, the Handala, was intercepted about 75km off Gaza in July.

The GSF’s boats set sail after experts from the UN-backed Integrated Food Security Phase Classification (IPC) confirmed that there was a famine in Gaza City and warned that it could spread to central and southern Gaza within weeks.

Gaza’s Hamas-run health ministry has said at least 440 Palestinians have died from the effects of malnutrition since the start of the war, including 162 since the famine declaration.

The UN has called on Israel to allow an unimpeded, large-scale humanitarian response that can save lives. As the occupying power, it has an obligation under international law to ensure sufficient food and medical supplies reach all of Gaza’s population.

Israel has insisted it acts in accordance with international law and facilitates the entry of aid.

It has also disputed the IPC’s findings and the health ministry’s figures, and strongly denied the allegation – most recently made by a UN commission of inquiry – that its forces have committed genocide against Palestinians in Gaza.

The Israeli military launched a campaign in Gaza in response to the Hamas-led attack on southern Israel on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

At least 65,419 people have been killed in Israeli attacks in Gaza since then, according to the territory’s health ministry.