The Norwegian activist Samuel Rostøl was awakened by an explosion during the night towards Wednesday, he tells the news agency NTB.
Within a few seconds, there was full activity on board. Security procedures in the event of an attack are something we have trained for and are prepared for, he says.
Rostøl is on board the boat Adara, one of a number of vessels in the convoy to Gaza, just south of the Greek island of Crete. The attack lasted for a few hours and was "very unpleasant", he says.
We saw a small light from a very fast drone that flew over the smaller sailboats in the flotilla. At regular intervals, it flashed, followed by the sound of an explosion a few meters above the deck.
Italy sends assistance
At least 13 explosions were heard on or around the vessels, according to activists for AP. According to the news agency's information, "unidentified objects" were dropped on at least ten of the boats.
No personal injuries have been reported and Israel has not commented.
On Wednesday afternoon, Italy strongly condemns the attack on the convoy. In a statement, Defense Minister Guido Crosetto says he has redirected an Italian naval vessel to offer assistance and protection.
Later on Wednesday, Spanish Prime Minister Pedro Sánchez announced that the Spanish Navy is also sending a vessel for the same purpose.
We are concerned, so we are deploying a vessel to ensure that our citizens, if necessary, can be put to safety and taken back to Spain, says Sánchez in New York, where he is attending the UN General Assembly.
The UN human rights organization OHCHR is simultaneously demanding an independent investigation into the reported drone attacks, writes AFP.
"There must be an independent, impartial and thorough investigation of the reported attacks and harassment from drones and other objects", says Thameen Al-Kheetan, spokesperson for OHCHR, in a statement.
Photos with Hamas representatives
Global Sumud Flotilla (GSF) aims to sail to the Gaza Strip with humanitarian aid and thus break the Israeli blockade of the area.
Earlier in September, GSF also reported that the convoy had been attacked by drones, then off the coast of Tunisia.
Israel has repeatedly accused GSF of being a terror-linked "jihad initiative" that serves the Hamas agenda. The allegations come after some of the representatives of GSF's steering group were seen in pictures together with representatives of Hamas, Islamic Jihad and the Popular Front for the Liberation of Palestine (PFLP), all of which are classified as terrorist organizations by the US and EU.
