Israel unleashed new round of heavy air strikes on Gaza City earlier on Monday, after destroying several homes on Sunday and bombing the house of Hamas’ Gaza leader.

Monday’s explosions rocked the Gaza City from north to south for 10 minutes in an attack that was heavier, on a wider area and lasted longer than a series of air raids 24 hours earlier.

The earlier Israeli airstrikes flattened three buildings and killed at least 42 people Sunday, Palestinian medics said. It was the deadliest single attack in the latest round of violence between Israel and the Hamas that rules Gaza.

Both Israel and Hamas faced mounting international calls for a ceasefire in hostilities that entered their second week on Monday with no end in sight.

However, Israeli Prime Minister Benjamin Netanyahu said on Sunday that the Israeli air strikes and shells in the Gaza Strip "will continue as long as necessary".

In a televised statement in the Defense Ministry in Tel Aviv, Netanyahu downplayed international pressures on Israel to agree to a truce that will quell the escalation, which has so far cost the lives of hundreds of Palestinians in Gaza and dozens in Israel.

UN Secretary-General Antonio Guterres pleaded for an immediate end to the "utterly appalling" violence and warned of an "uncontainable security and humanitarian crisis".

Chinese State Councilor and Foreign Minister Wang Yi on Sunday also called for the international community to move forward with urgency to prevent the situation from further deteriorating, to prevent the region from falling again into turmoil, and to protect the lives of local people.

Xinhua and agencies