Israeli naval forces intercepted a Gaza-bound aid flotilla on Monday, boarding dozens of vessels off the coast of Cyprus in the latest attempt by activists to breach Israel’s maritime blockade of the territory.

The convoy, organised by an international movement calling itself the Global Sumud Flotilla, comprised more than 50 boats that had set sail from the Turkish port of Marmaris the previous week. Organisers described the voyage as the final stage of a mission to deliver humanitarian supplies to Palestinians in Gaza.

The flotilla said Israeli military personnel boarded several of its boats roughly 250 nautical miles from Gaza, in waters beyond Cypriot territorial limits. Unlike earlier interceptions, which mostly took place at night, the boarding was carried out in daylight.

Israel’s foreign ministry said it would “not allow any breach of the lawful naval blockade on Gaza,” a position the government has maintained throughout a series of similar attempts to reach the territory by sea.

Turkey’s foreign ministry condemned the operation as an “act of piracy” and said Ankara was taking steps, in coordination with other governments, to secure the safe return of Turkish citizens aboard the convoy. Organisers said a Polish participant had also been detained.

Israel imposed a naval blockade on Gaza years ago, citing the need to prevent weapons from reaching armed groups in the territory. Aid organisations and activists argue the restrictions have worsened a humanitarian crisis among Gaza’s population.

Previous flotillas have been halted in much the same way, with passengers detained and later deported, and the vessels and their cargo impounded. Organisers said they intended to continue mounting such missions.