Israel's foreign ministry has branded it a "selfie yacht", while Thunberg says she has been "kidnapped" after Israeli forces boarded the vessel.

The British-flagged yacht Madleen, which is operated by the pro-Palestinian Freedom Flotilla Coalition, was aiming to deliver symbolic aid to Gaza.

In a pre-recorded video released by the Freedom Flotilla Coalition Thunberg said: "If you see this video, we have been intercepted and kidnapped."