Israel’s navy Saturday seized a Swedish-flagged sailboat carrying activist passengers that was trying to breach the long-standing blockade of the Palestinian Gaza Strip.

The Israeli military said the vessel, named “Freedom for Gaza,” was “intercepted in accordance with international law.”

The 12 passengers, from Sweden, Britain, Canada, France, Germany and Spain, are in custody and will be flown home, an Israeli Immigration Authority spokeswoman said.

The organizer of the trip, the Swedish group Ship to Gaza, said the boat was carrying mainly medical supplies and maintained it was wrongly intercepted in international waters.  

“The demands of the Ship to Gaza are that the ship with its crew and cargo … be allowed to go in peace through international and Palestinian waters in accordance with international law,” it said in a statement. “This is a demand that the 11 years-long illegal and destructive blockade on Gaza will be lifted at last.”

Israel’s military said the boat violated the “legal naval blockade” and that “any humanitarian merchandise can be transferred to Gaza through the Port of Ashdod.”

The vessel Freedom for Gaza was the second vessel of the “Freedom Flotilla” to be seized as it tried to “break the blockade” on Gaza, organizers said.

Earlier this week the Israeli navy intercepted a Norwegian-flagged activist boat, one of four that left Scandinavia in mid-May.

Israel contends the the blockade is necessary to keep Palestinian militants from getting weapons or other materials that could be used for military purposes.

Israel and Palestinian militants have fought three wars since 2008 in Gaza, an economically disadvantaged 365 square kilometer territory where more than two million Palestinians reside.

United Nations officials have called for the lifting of the blockade, citing worsening humanitarian conditions in the Palestinian enclave.