Witnesses said three rockets were fired at the Israeli settlement area of Sderot on Tuesday, where thousands of Israelis were demonstrating against their country's planned withdrawal from Gaza.
Two of the rockets reportedly fell in Palestinian areas and the third fell in an open field near Sderot.
Among the wounded were five children, aged four to 11, including four children of Hisham Abdel Razek, a senior official in the Fatah Party and a former Palestinian cabinet minister. Abdel Razek's wife was also wounded.
The dead boy was identified as Yasir Adnan Ashkar. His brother Ali, 11, was in a critical condition, hospital officials said.
One of the stray rockets fell on the brothers' home in the Bait Hanoun area, north east of Gaza City.
Abd al-Razek's wife and children were visiting her brother at the time, witnesses said.
Israeli convoy attacked
Minutes before the rockets were launched, an anti-tank rocket was fired at an Israeli convoy travelling to the Jewish settlement of Netzarim on Tuesday, Israeli settlers and the army said. There were no reports of injuries.
Palestinian residents nearby said the explosion, just south of Gaza City, was followed by gunfire. The Israeli occupation army said it was carrying out searches in the area.
Two Palestinian resistance movements, Islamic Jihad and the Popular Front for the Liberation of Palestine claimed responsibility for the attack on the convoy