Israel vowed on Sunday to prevent a ship carrying a dozen pro-Palestinian activists and some aid from reaching Gaza, saying its military would use “any means necessary” to prevent the vessel from breaching an Israeli naval blockade of the coastal enclave.

The civilian ship, called the Madleen, is operating under the auspices of the Freedom Flotilla Coalition, an international grass-roots campaign that opposes Israel’s nearly two-decade-long blockade of Gaza. The ship set sail from Sicily on June 1.

The boat’s tracker showed it off the coast of Egypt on Sunday, and the coalition said it was sailing “just 160 nautical miles from Gaza.” The passengers include the Swedish activist Greta Thunberg and Rima Hassan, a member of the European Parliament.

Israel imposed the blockade on Gaza, with Egypt’s help, after Hamas, the Islamic militant group, took over the coastal strip in 2007. Israeli officials have said the blockade is necessary to prevent weapons smuggling into the enclave.

Conditions in Gaza have worsened considerably since the deadly Hamas-led attack on Israel in October 2023, which ignited the current war, now in its 20th month. Israel recently barred the entry of any humanitarian aid for 80 days, bringing the territory to the brink of famine, according to international aid organizations.

The Madleen is probably carrying only a symbolic amount of humanitarian aid. The coalition said in a statement that it was bringing urgently needed goods, including baby formula, flour, rice, diapers, medical supplies and children’s prosthetics.