Activists who were planning to sail an aid ship to Gaza say it was struck by drones in international waters off the coast of Malta – and appeared to accuse Israel of being behind the attack.

The Freedom Flotilla Coalition said its ship The Conscience was targeted at 00:23 local time on Friday and issued an SOS signal right after the attack. The group said it had planned to sail to Gaza and “challenge Israel’s illegal siege and blockade” there.

The Maltese government said a fire onboard the ship was “brought under control overnight” and that no casualties had been reported.

It that said 12 crew and four activists were on board the boat, while the NGO said 30 activists had been on board.

The NGO called for Israeli ambassadors to be summoned to answer for “violation of international law, including the ongoing blockade and the bombing of our civilian vessel”.

The Israeli military said it was looking into reports of the attack.

The Freedom Flotilla Coalition uploaded a video showing a fire on one of its ships but did not indicate whether anyone had been hurt. It said the attack appeared to have targeted the generator, which left the ship without power and at risk of sinking.

The ship was 17 nautical miles (31.5 kilometres) east of Malta when it was hit.

Cyprus responded to the SOS signal by dispatching a vessel, the charity said, but that it was not “providing the critical electrical support needed”.

The coalition is campaigning to end Israel’s blockade of Gaza.

Two months ago, Israel shut all crossings to Gaza – preventing all goods, including food, fuel and medicines from entering – and later resumed its military offensive, ending a two-month ceasefire with Hamas.

The Israeli military launched a campaign to destroy Hamas in response to an unprecedented cross-border attack on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

At least 52,418 people have been killed in Gaza during the ensuing war, according to the territory’s Hamas-run health ministry.