Israeli air strikes targeted Jabalia, Gaza’s largest refugee camp, for the second time in two days on Wednesday. As rescue workers clawed through the rubble and footage showed smoke billowing above the camp, there was no immediate confirmation on the number of casualties.

In Tuesday’s attack, the Hamas-run health ministry said that more than 50 people were killed. Israel claimed to have killed a Hamas commander in that strike.

The densely populated camp in the north of the besieged enclave covers an area of 1.4 square kilometres (0.5 sq miles). According to the United Nations, there are some 116,000 registered refugees in the camp.

UN humanitarian chief Martin Griffiths denounced the Jabalia strike after a two-day visit to Israel and the occupied Palestinian territories.

“This is just the latest atrocity to befall the people of Gaza where the fighting has entered an even more terrifying phase, with increasingly dreadful humanitarian consequences,” Griffiths said in a statement.

He said “the world seems unable, or unwilling, to act”, adding “This cannot go on. We need a step change.”

Griffiths said: “We need the warring parties to agree to pauses in the fighting” so that desperately needed aid can get into the Palestinian territory of 2.3 million people.

Israel’s military later issued a statement saying the country’s fighter jets had struck a Hamas command-and-control complex in Jabalia “based on precise intelligence”, killing the head of the Islamist group’s anti-tank missile unit, Muhammad A’sar.