Activist Greta Thunberg and retired US Army Colonel Mary Ann Wright were among 40 humanitarians - including Maltese nationals - preparing to board a Gaza aid mission vessel on Friday.

The mission was stopped short because of a fire on the Conscience that the Gaza Freedom Flotilla said was caused by a drone attack just outside Maltese waters.

In comments to Times of Malta Thunberg said the incident was "yet another crystal clear example of how international law and human rights are being completely disrespected".

Thunberg added that "too many people are being deliberately starved in Gaza by Israel", and it is everyone's responsibility to do everything in their power to try to stop that. 

The team in Malta waiting to board was "incredibly worried for our comrades" on the boat, and many were shocked that the attack happened so close to an EU country, the young activist said. 

The Conscience is taking part in a mission to highlight Israel's siege on the Palestinian enclave and transport humanitarian aid to Gazans.

Activists in Malta told Times of Malta they have tried to board the vessel for some days now, but were not given the go-ahead by the local authorities. On Thursday, Palau removed the vessel from its ship register.

Hours later, the crew aboard reported a fire which it said was caused by two drone attacks, resulting in a fire and a breach in the hull.

They sent out an SOS distress signal, with the Maltese government noting that a nearby tug boat put out the fire after confirming with Malta Vessel Traffic Services that it had firefighting equipment. 

An Armed Forces of Malta patrol vessel was also dispatched to provide further assistance, but the people aboard the Flotilla boat refused to move to the tug vessel.

They need to remain aboard the vessel, loaded with humanitarian aid, as it is their responsibility to make sure it remains afloat.

The ship remains outside territorial waters and is being monitored by the competent authorities, the government added.