The activists had set out to protest Israel’s ongoing military campaign in the Gaza Strip, which is among the deadliest and most destructive since World War II, and its restrictions on the entry of aid.

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

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