The U.S. government on Thursday asked Egypt to use its influence with the Palestinians to calm the escalating violence in Gaza.

"We ask Egypt to use its influence in the region to help de- escalate the situation," State Department spokesman Mark Toner said at a regular briefing.

Regarding the escalation of violence in Gaza, Toner put the blame on Hamas, urging the Islamist group to stop its rocket attacks into Israeli territories.

"This is a situation that they've created by firing rockets on innocent Israeli civilians. You know, we obviously mourn civilian deaths on both sides. But the onus is on Hamas to stop its rocket attacks," he said.

Israel has been attacking targets in Gaza for the past 30 hours. On Wednesday afternoon, the Israeli Air Force targeted Hamas military chief Ahmed Jabri and killed him.

According to the Palestinians, 15 have been killed so far and more than 40 wounded.

Meanwhile, some 250 rockets were launched toward Israel's southern communities in the past 24 hours. Three Israelis were killed Thursday morning when a rocket slammed into an apartment building in the southern city of Kiryat Malachi.

In a press gaggle en route to New York on Thursday, White House spokesman Jay Carney strongly condemned the rocket attacks launched by Hamas and regretted the deaths and injuries of innocent Israeli and Palestinian civilians.

On Wednesday, U.S. President Barack Obama spoke by phone separately with Israeli Prime Minister Benjamin Netanyahu and Egyptian President Mohamed Morsi about the escalating violence in Gaza.

In both conversations, Obama reiterated U.S. support for Israel 's right to self-defense, while urging Netanyahu to make every effort to avoid civilian casualties.

Egyptian President Morsi stressed Thursday the necessity of stopping Israeli aggression on the Gaza Strip. A day earlier, he decided to call back the Egyptian ambassador to Israel.