Israel’s defense minister has vowed to prevent an aid boat carrying Greta Thunberg and other activists from reaching the Gaza Strip.

Defense Minister Israel Katz said Sunday that Israel wouldn't allow anyone to break its naval blockade of the Palestinian territory, which he said was aimed at preventing Hamas from importing arms.

Thunberg, a climate campaigner is among 12 activists aboard the Madleen, which is operated by the Freedom Flotilla Coalition. The vessel departed Sicily last Sunday on a mission that aims to break the sea blockade of Gaza and deliver humanitarian aid, while raising awareness over the growing humanitarian crisis in the Palestinian enclave, The AP news reported.

The activists had said they planned to reach Gaza’s territorial waters as early as Sunday.

Rima Hassan, a French member of the European Parliament who is of Palestinian descent, is among the others onboard. She has been barred from entering Israel because of her opposition to Israeli policies toward the Palestinians.

After a three-month total blockade aimed at pressuring Hamas, Israel started allowing some basic aid into Gaza last month, but humanitarian workers have warned of famine unless the blockade and the war end.

An attempt last month by Freedom Flotilla to reach Gaza by sea failed after another of the group’s vessels was attacked by two drones while sailing in international waters off Malta. The group blamed Israel for the attack, which damaged the front section of the ship.