US President Barack Obama said on Monday the world must focus on a cease-fire in the Palestinian-Israeli conflict to put an end to the rising number of civilian casualties.

The Palestinian death toll in an Israeli offensive in the Gaza Strip rose above 500 on Monday. Hamas, which killed 13 Israeli soldiers in Gaza on Sunday in the biggest one-day toll in eight years, continued to fire rockets deep into Israel.

Obama repeated that Israel had the right to defend itself against onslaughts from Hamas militants but said he had serious concerns about the growing number of civilian deaths resulting from the conflict.

"As I've said many times, Israel has a right to defend itself against rocket and tunnel attacks from Hamas. And as a result of its operations, Israel has already done significant damage to Hamas's terrorist infrastructure in Gaza," Obama told reporters at the White House.

"I've also said, however, that we have serious concerns about the rising number of Palestinian civilian deaths and the loss of Israeli lives, and that is why it now has to be our focus and the focus of the international community to bring about a cease-fire that ends the fighting and that can stop the deaths of innocent civilians," he said.

Please LIKE our Facebook page - it makes us stronger