Israeli planes renewed air strikes in Gaza early on Saturday and Hamas militants responded by firing rockets.
Palestinian medics said at least four people were killed in one of several air strikes in northern Gaza. Residents said Israeli naval boats fired shells from the Mediterranean though none may have hit the strip.
The Palestinian religious affairs ministry said Israeli planes destroyed a mosque. A military spokesman said the army was checking the report.
Sirens sounded in two major southern Israeli cities warning of incoming fire from Gaza. Hamas claimed responsibility for launching rockets.
With no sign of an end to the fighting, casualties spread further afield, with Palestinians reporting 11 killed in the occupied West Bank amid clashes between protesters and Israeli security forces.
At least 132 people have been killed in Gaza since Monday, including 32 children and 21 women, and 950 others wounded, Palestinian medical officials said.
Hamas said a woman and a boy were among four people killed in an Israeli air strike that hit a home belonging to the Abu Hattab family in Gaza City’s Beach refugee camp.
The Israeli army did not immediately respond to a request for comment on the strike