Israel’s military operation against Palestinian Hamas militants in Gaza will continue “with full force”, Prime Minister Benjamin Netanyahu has said.
“We are acting now, for as long as necessary, to restore calm… It will take time,” Mr Netanyahu warned.
Gaza officials said 42 people, including 16 women and 10 children, died in the latest Israeli air strikes.
Ten people, including two children, have been killed in rocket attacks on Israel since Monday, Israel said.
The overall death toll in Gaza now stands at 188 people, including 55 children and 33 women, with 1,230 injured, according to the Hamas-controlled health ministry. Israel says dozens of militants are among the dead.
Israel’s military says it has been targeting leaders and infrastructure linked to Hamas.
Hamas launched a new barrage of rockets towards southern Israel on Sunday afternoon.
Meanwhile, the UN Security Council is holding an emergency meeting, with international mediators hoping to broker a ceasefire.
UN Secretary General Antonio Guterres opened the meeting by describing the violence as “utterly appalling” and said the fighting must stop immediately.
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The Israeli air strikes – the deadliest attack in the conflict so far – hit a busy street just after midnight on Sunday.
Palestinian rescue workers have been working through the rubble of at least three destroyed buildings, pulling out bodies and searching for survivors.
“I have never covered air strikes with such intensity, explosions are everywhere in Gaza, there are difficulties in communicating with officials to find out where the strikes are,” said the BBC’s Rushdi Abualouf in Gaza.
“The building in which I live in [the] western part of the city shook like an earthquake,” he wrote on Twitter. “A hysterical state of chaos, children and women in the building that houses more than 200 people screaming.”
Israel’s military said it struck the homes of both Hamas leader Yahya Sinwar and his brother Muhammad Sinwar, whom it described as head of logistics and manpower for the movement.