Update | Israeli onslaught claims 121st victim in Gaza as Obama offers to help broker truce

Israel's bombardment of Gaza claimed its 121st Palestinian life on Saturday as Hamas pounded central Israel with rockets and Washington offered help brokering a truce.

As the battle between Israel and Hamas militants entered its fifth day, diplomatic efforts to end the hostilities gathered pace.

Overnight, US President Barack Obama phoned Israeli Prime Minister Benjamin Netanyahu to express concerns and to offer his help in resolving the crisis.

"The United States remains prepared to facilitate a cessation of hostilities, including a return to the November 2012 ceasefire agreement," the White House said, referring to a truce which ended the last major confrontation between Israel and Hamas.

But Egypt, which has played a key role in mediating previous ceasefire agreements, said its efforts were falling on deaf ears.