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

Thunberg, a climate campaigner, is among 12 activists aboard the Madleen, which aims to break the blockade of Gaza and deliver humanitarian aid.

The almost 20 months of war has torn Gaza apart, often displacing residents multiple times and killing more than 54,000 people, according to the Hamas-run Health Ministry. A U.S.-brokered ceasefire agreed in January collapsed in March as Israel enforced a blockade on all humanitarian aid into the strip.