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.

The blast left large craters surrounded by wrecked buildings. Israel repeatedly warned Gaza residents to evacuate northern areas and while many have gone south, many have stayed.

Israel besieged Gaza after the Hamas attack, and the UN and other aid officials said civilians in the enclave were living in a public health catastrophe, with hospitals struggling to treat casualties as electricity supplies petered out.

On Wednesday, communications and internet services were completely cut off in the enclave again, Gaza's largest telecommunications provider Paltel said.

In Washington, a group of anti-war protesters raised red-stained hands to interrupt a hearing in Congress on providing more aid to Israel. They shouted slogans including, "Cease-fire now!" "Protect the children of Gaza!" and "Stop funding genocide." Capitol police removed them from the room.

Power generators in Al Shifa Medical complex and the Indonesian Hospital in Gaza will run out of fuel in a few hours, Ashraf Al-Qidra, spokesperson for the health ministry in Gaza said. He called on petrol stations owners in the enclave to urgently feed the two hospitals with fuel if possible.

After the attack on Jabalia, dozens of bodies lay shrouded in white, lined up against the side of the Indonesian Hospital, footage obtained by Reuters showed.

Juggling dwindling supplies of medicines, power cuts and air or artillery strikes that have shaken hospital buildings, surgeons in Gaza have worked night and day trying to save a constant stream of patients.

"We take it an hour at a time because we don't know when we will be receiving patients. Several times we've had to set up surgical spaces in the corridors and even sometimes in the hospital waiting areas," Dr. Mohammed al-Run said.

Iran-backed Hamas has told mediators it will release some foreign captives in the coming days, Abu Ubaida, the spokesperson of the group's armed wing, al-Qassam Brigades, said in a video on the Telegram app Tuesday. He gave no further details on the number of captives or their nationalities.

Meanwhile, Israeli families of victims of the Oct. 7 attack appealed to the International Criminal Court on Tuesday to order an investigation into the killings and abductions. Israel is not a member of the Hague-based court and refuses to recognize its jurisdiction.

The United States has made "real progress" in the last few hours in negotiations to secure a safe passage for Americans and other foreign nationals who wish to leave Gaza, US State Department spokesperson Matthew Miller said.

US Secretary of State Antony Blinken will visit Israel on Friday for meetings with members of the government and then make other stops in the region, the department said.

On Tuesday, Blinken said the United States and other countries were looking at "a variety of possible permutations" for the future of Gaza if Hamas militants are removed from control. Israel has vowed to annihilate Hamas after several inconclusive wars dating back to the militant group's 2007 takeover of Gaza.

Israeli Prime Minister Benjamin Netanyahu dismissed international calls for a "humanitarian pause" in fighting to enable emergency aid deliveries to civilians suffering from critical shortages of food, medicine, drinking water and fuel.

The US, Qatar and Egypt have been working to open the Rafah crossing into Egypt to allow people to come and go.

Egyptian authorities would allow 81 Gazans who were severely wounded in the weeks of bombardment to enter Egypt on Wednesday to complete treatment, the Palestinian border authority said. (Reuters-Yonhap)