Health ministry officials in Gaza told Xinhua that two teenagers were killed by Israeli artillery fire in the northern Gaza Strip city of Biet Hanoun.
A five-month infant was killed and his mother injured when an Israeli warplane destroyed their house in the southern Gaza Strip city of Rafah, medics said.
According to the same sources, a man was also killed in the same area. Two young men were killed by artillery shelling in Gaza-Israel border areas.
On July 8, Israel started an all-out aerial operation, dubbed "Protective Edge", to stop rocket fire from Gaza. So far, 246 Palestinians have been killed and more than 1,850 others injured in the operation.
Israeli Prime Minister Benjamin Netanyahu on Thursday ordered a ground operation in the Hamas-ruled Gaza Strip.
Netanyahu's decision came after Egyptian and international efforts to reach a ceasefire failed. Hamas warned that Israel would pay a heavy price for its ground offensive on Gaza.