Israeli media say Israel's navy has attacked a six-ship aid convoy carrying pro-Palestinian activists to the Gaza Strip, killing at least 10 people.
A private Israeli television station said Israeli forces intercepted the flotilla early Monday and fired on at least one of the vessels.
Turkey's NTV television aired images from the ships of several people who were said to be wounded.
Israel has warned it will not allow the flotilla to reach Gaza, which has been under a blockade by Israel and Egypt since 2007 when Palestinian militant group Hamas seized control of the territory.
Three Israeli missile boats left their base in Haifa late Sunday to prevent the ships from entering the 32-kilometer exclusion zone Israel enforces along Gaza's Mediterranean Sea coast.
The aid ships, carrying more than 600 pro-Palestinian activists and 10,000 tons of supplies, left for Gaza on Sunday and defied a radio warning from the Israeli navy not to approach the region. An Israeli official said the navy told them they were approaching a blockaded area and asked them to go to the Israeli port of Ashdod or turn back.
Organizers from the Free Gaza Movement and a Turkish human rights group say the convoy, which includes three cargo ships and three passenger boats, is carrying medical supplies as well as cement and other building materials, which Israel has banned from entering Gaza due to security concerns.
The activists say the construction supplies are intended to help Gazans rebuild homes destroyed during Israel's military offensive in the Islamist-controlled territory early last year.
U.N. officials and international aid groups say Israel's three-year blockade on Gaza has devastated the local economy and failed to weaken Hamas grip on power.
Some information for this report provided by AP, AFP and Reuters.