GAZA - The Palestinian interior ministry in Gaza accused Egyptian forces on Saturday of killing a mentally-ill Palestinian who had waded through the sea into Egypt's territory.The incident happened on Friday, Gaza's interior ministry said. Video broadcast by Al-Jazeera network showed the man walking in the Mediterranean sea, naked, and then crossing through a wire fence into Egyptian territory before he is fired at several times while still in the water. Another person on the beach appears to signal to security forces at a watchtower to stop shooting and the man's body is seen floating in the water and then washed up on shore.The Egyptian Interior Ministry had no immediate comment.Gaza is ruled by the Islamist Hamas group. The Interior Ministry there said the man was mentally ill and demanded Egypt launch a probe into the incident. "It is clearly a cold-blooded execution, committed in broad day light," spokesman Eyad al-Bozom said.Egypt and Hamas, an offshoot of the Muslim Brotherhood, have tense relations.The Egyptian Muslim Brotherhood was ousted from power when former president Mohamed Morsi was overthrown in 2013. The Egyptian government has accused Hamas of helping Islamist militants in Egypt's Sinai desert, which borders Gaza. Hamas denies this.