Israeli airstrikes hit a densely populated refugee camp in the Gaza Strip, killing at least 50 Palestinians and a Hamas commander, and medics struggled to treat the casualties in the enclave where food, fuel and basic supplies are running scarce.

Israeli tanks have been active in Gaza for at least four days following weeks of air bombardments in retaliation for an attack by Palestinian Hamas militants on southern Israeli towns on Oct. 7 and the taking of more than 200 hostages.

An Israel Defense Forces statement said the strike by fighter jets on Jabalia, Gaza's largest refugee camp, had killed Ibrahim Biari, a Hamas commander it said was "pivotal" in the planning and execution of the attack.

Dozens of Hamas combatants were in the same underground tunnel complex as Biari and were also killed when it collapsed in the attack, IDF spokesperson Lt. Col. Jonathan Conricus said, adding: "I understand that is also the reason why there are many reports of collateral damage and non-combatant casualties. We're looking into those as well."

Hamas spokesperson Hazem Qassem denied any senior commander was in the camp, and called the claim an Israeli pretext for killing civilians. Palestinian health officials said at least 50 Palestinians were killed and 150 wounded.

A Hamas statement said there were 400 dead and injured in Jabalia, which houses families of refugees from wars with Israel dating back to 1948. Reuters could not independently verify the reported casualty figures.