Thunberg, a climate campaigner, is among 12 activists aboard the Madleen, which aims to break the blockade of Gaza and deliver humanitarian aid.

Activist Yasemin Acar has revealed just how close the Freedom Flotilla's Madleen ship is to reaching Gaza. She warned that herself, Greta Thunberg and others could be intercepted at any moment - track

There are a number of things that could cause the ship to turn around, like lack of food and water or problems with the engine.