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 197 people, including 58 children and 34 women, with 1,235 injured, according to the Hamas-controlled health ministry. Israel says dozens of militants are among the dead.
Meanwhile, the UN Security Council held an emergency meeting, with international mediators hoping to broker a ceasefire.
UN Secretary General António Guterres opened the meeting by describing the violence as "utterly appalling" and said the fighting must stop immediately.
Sunday was the deadliest day so far
The Israeli air strikes hit a busy street in Gaza just after midnight on Sunday, causing at least three buildings to collapse and dozens of deaths.
Hamas launched barrage of rockets towards southern Israel overnight and during the afternoon.
Millions of Israelis scrambled to safe rooms or shelters as sirens went off. Palestinians also tried to take precautions, but in the densely packed and poorly resourced Gaza Strip, many had nowhere to go.
Riyad Eshkuntana told Reuters news agency he put his daughters to sleep in a room of his house that he thought was the furthest from the explosions. Only one of his daughters, Suzy, six, survived the night. His wife and three other children died.