Palestinians work on the rescue of a casualty at the site of Israeli strikes on houses in Jabalia refugee camp in the Gaza. Reuters

Israeli airstrikes hit a densely populated refugee camp in the Gaza Strip, at least 400 dead and injured, according to a Hamas statement said on Wednesday.

An Israel Defence Forces (IDF) 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.

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.

Bodies of Palestinians killed in Israeli strikes on houses in Jabalia refugee camp, lie at a hospital in Gaza. Reuters

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.

Public health crisis engulfs Gaza

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, "Ceasefire now!" "Protect the children of Gaza!" and "Stop funding genocide." Capitol police removed them from the room.

Palestinians search for casualties at the site of Israeli strikes on houses in Jabalia refugee camp in Gaza. Reuters

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 in Gaza, footage obtained by Reuters showed.

Reuters