One child was killed and two others were wounded when a rocket landed on their home near the border with Gaza, security and medical sources told Reuters.
Sara Salama, 13, died while her brother Khaled, eight, and two-year-old sister Rahaf sustained serious injuries when the rocket hit the town of el-Mattallah south of Rafah.
A Hamas spokesman has denied any rockets were fired from the Gaza strip.
There have been two days of quiet in Gaza. No rockets or missiles, no more destroyed houses, no more ambulance sirens screaming.
A three-year-old girl has been rescued from Gaza and brought to London for life-saving heart surgery.
A small team of NHS doctors and surgeons is travel to Gaza to set up facilities and establish how best to use specialists and equipment.