The Israeli army said at least four soldiers were "lightly injured" on Sunday, as they attacked a site in northern Gaza the army said was being used to launch long-range rockets.
"During the mission a gunfight broke out..., during which four Israeli soldiers were lightly wounded," said the spokesman who declined to give further details on the operation.
The Qassam Brigades, Hamas' armed-wing, confirmed the exchange of gunfire "between our fighters and soldiers of the Zionist navy which tried to penetrate the zone of Sudanyia" in northwest Gaza.
The early morning incursion followed the deadliest night of Israeli bombing since it launched its campaign on Tuesday. A total of 52 Palestinians were reported killed overnight, bringing the toll to 165 in six days of attacks.
Eighteen people, many from the same family, were killed in the deadliest attack when Israeli forces targeted the home of Gaza police Chief Tayseer al-Batsh in the Toufah area of Gaza City.
Batsh was among the wounded, Palestinian officials told AFP.
The UN Security Council called for a cessation of hostilities and top diplomats from the UK, France, Germany and the US are due to meet later on Sunday to discuss the need for a ceasefire.