Israeli navy forces boarded most of the vessels and detained dozens of activists and a number of European lawmakers aboard a flotilla attempting to break Israel’s blockade of Gaza on Thursday.

Greta Thunberg, a climate activist who was on board one of the vessels, released a video saying she had been "abducted" by Israeli forces.

"Our humanitarian mission was non-violent and abiding by international law. Please tell my government to demand my and the others' immediate release," she added.

The Global Sumud Flotilla, made up of more than 40 boats and 500 activists, was carrying a symbolic amount of humanitarian aid to Gaza.

The organizers of the flotilla said one boat had managed to sail on but had stopped near Gaza’s coast on Thursday morning before contact with the vessel was lost.

They said 39 of their boats were intercepted — or assumed intercepted as communication with the activists was lost — in an Israeli operation that began the night before.

Unlike previous sea attempts, this flotilla was the largest yet to try and break the Israeli blockade of Gaza.

The activists said they believed that with the sheer number of boats, it would be more difficult for Israeli authorities to intercept them all.