The IDF had boarded the Gaza Freedom Flotilla, Madleen, the ship's operators said on Telegram early Monday morning at around 3 a.m., with everyone on board reportedly arrested.
The IDF had previously estimated that the flotilla would arrive in Israeli territory an hour earlier.
The Madleen's official tracker showed the ship edging closer to the Gaza coastline. The IDF's naval unit, Shayetet 13, has already begun training for the ship’s boarding.
At 1:17 a.m., the flotilla's Telegram account reported that alarms sounded on the ship, and life jackets were being prepared. The activists on board include Greta Thunberg, European lawmaker Rima Hassan, and Game of Thrones actor Liam Cunningham.
One of the flotilla participants, Yasmine Najer, uploaded a video to her Instagram and explained why the alarm in the flotilla was activated: "We are very close to Gaza. The reason we activated the alarm is that four ships surrounded us and two approached to a distance of about 200 meters - this has not happened before. So that is why we sounded the alarm.