An international charity, the Free Gaza Movement, says its boat laden with medical aid for Gaza has been intercepted by five Israeli naval vessels in international waters off the coast of south Lebanon and forced to return to Cyprus.
The boat, The Spirit of Humanity, is reported to have 21 people on board, including doctors and European Members of Parliament.
Meanwhile, Israeli negotiator Amos Gilad has arrived in Cairo to talk with Egyptian mediators about a possible truce in the Gaza conflict.
A Hamas delegation ended several days of talks in Cairo on Wednesday saying it had given the Egyptians its comments on an Egyptian peace plan that includes securing the Egypt-Gaza border and ending the Israeli blockade of Gaza.
An Israeli government spokesperson, Mark Regev, says the talks have what he calls momentum. But he says Israel will not agree to a truce that would allow Hamas to regroup and rearm.
A 10-day ceasefire has been proposed, and with the Gaza death toll still climbing, UN Secretary General Ban Ki-Moon says there is no time to lose.
The Palestinian health ministry says at least 320 of the 1000 Palestinians killed in the current fighting have been children.
Nearly 5000 people have been injured or wounded.
Hamas head appeals directly to West
The head of Hamas's government in Gaza, Ismail Haniyeh, has made a direct appeal to Western readers to press for an end to Israel's military offensive.
Writing in the British newspaper the Independent, Mr Haniyeh says Hamas will accept a ceasefire under "clear and simple" conditions -- the lifting of the blockades on Gaza, the opening of the crossings and Israel's complete withdrawal.
He rejects claims Hamas is to blame for the conflict by refusing to renew a six-month ceasefire in December, saying Israel has made life in the Gaza Strip a "living hell" through economic "strangulation".