A Gaza-bound activist aid ship caught fire and issued an SOS, after what it claimed was a drone attack off the coast of Malta in international waters.

Axar.az reports the Freedom Flotilla Coalition (FFC), which is campaigning to end Israel’s blockade of Gaza, told CNN activists were aboard its ship carrying humanitarian aid when the alleged attack happened just after midnight local time Friday (6 p.m. ET Thursday).

The ship, the Conscience, was heading to Malta, where a large contingent of activists were due to board before it departed for Gaza, but had not made it into port, the group said.

FFC said it had been operating under a media blackout over the mission because it wanted to avoid potential sabotage.

The group pointed the finger of blame at Israel, without providing evidence.

The Armed Forces of Malta confirmed there had been a fire on a ship that has now been extinguished. “We are monitoring the situation closely,” a spokesperson told CNN, adding that there were no injuries onboard.

In a later statement, Malta’s government said a tug boat had been send to assist the vessel. It said the aid ship, the Conscience, had 12 crew members and 4 civilian passengers on board.

“All crew were confirmed safe but refused to board the tug. Assistance was provided to support interior firefighting efforts,” the Maltese government statement said.

Marine traffic websites show the ship, the Conscience, departed Tunisia on Tuesday night. Tracking data showed it had been in its position off the coast of Malta for around 12 hours before the alleged attack occurred on Friday morning. The Conscience is listed as flying under a Palau flag.

FFC’s lead organizer, Thiago Avila, told CNN the organization was now trying to arrange a small boat to accompany a rescue crew to the location of the Conscience.

The Freedom Flotilla Coalition describes itself on its website as an international network of pro-Palestinian activists working to end Israel’s blockade of Gaza and deliver humanitarian aid to the besieged enclave by taking direct, non-violent action.