JERUSALEM (CNN) - As rockets and missiles fly back and forth between Gaza and Israel, the Israeli military is preparing for a possible ground incursion.
Israel Defense Forces said air strikes hit about 160 targets in Gaza early Wednesday, and 150 air strikes were carried out the day before.
Also Wednesday, the IDF said its Iron Dome defense system had intercepted 56 of the 255 rockets fired out of Gaza in recent days. The remaining rockets were allowed to fall on unpopulated areas.
Israeli Intelligence Minister Yuval Steinitz told CNN a ground operation "might become necessary," and Defense Minister Moshe Ya'alon said the security operation against the militant group Hamas "will probably not end within several days."
On Tuesday, the Israeli Cabinet authorized the military to call up 40,000 troops if needed. That is 10,000 more than were called up during Israel's offensive into Gaza in November of 2012. Only about 1,000 have been mobilized so far.
"I hope that it's not going to escalate into an all-out war," said Maen Rashid Areikat, the Palestinian representative to the United States. "For the Israelis, they have to know that there's no military solution to this problem."
Recent days have brought a dramatic escalation in the conflict.
Palestinian officials said Wednesday that at least 37 people in Gaza had been killed and more than 300 injured in Israeli air strikes since Operation Protective Edge began Monday.
Earlier, the Palestine Red Crescent Society said it had treated 678 wounded people. And Defense for Children International-Palestine said eight of the dead were children.
Rocket attacks into Israel are nothing new, but their reach has grown.
Warning sirens that blared Tuesday in Tel Aviv, one of Israel's most populated areas, showed a threat Israel had warned of. The country said militants' rockets from Gaza are powerful enough to reach 3.5 million Israeli residents.
The attacks sent U.S. Embassy personnel in Tel Aviv scurrying to an underground shelter, U.S. officials told CNN. It was just a precautionary measure, they said.
Lt. Col. Peter Lerner, a military spokesman, said Hamas is estimated to have 10,000 rockets of varying ranges, including some that can reach as far north as Tel Aviv and beyond.
Israel confirmed that a rocket hit the city of Hadera, which is some 62 miles (100 kilometers) from Gaza.
Islamic Jihad, another Palestinian militant group, took responsibility for the rocket fired at Tel Aviv. In a statement, the group called it a "response to the ongoing Zionist aggression."
"The Palestinian people will defend themselves," said Osama Hamdan, a foreign policy spokesman for Hamas. If there is a "clear cease-fire, the Palestinians will deal with that."
Hamas later claimed responsibility for firing rockets on Jerusalem and Haifa. There were no immediate reports of casualties.
Jerusalem Mayor Nir Barkat said he finds the rocket attacks surprising.
"It is amazing to find terrorist groups that are willing to fire indiscriminate rockets targeted at civilians," he said.
Tensions in the region reached a fever pitch after three Israeli teens, including one with dual U.S. citizenship, were kidnapped last month on their way home from school in the West Bank. Their bodies were found last week.
Israel blames Hamas, but the group has denied any involvement.
"Hamas said it clearly, We don't have information about what had happened," Hamdan told CNN's Michael Holmes.
Only days after the bodies of the Israelis were discovered, a Palestinian teen was abducted, and then found dead, within an hour in Jerusalem. Israel has arrested suspects and says there's "strong indication" it was a revenge killing.
Palestinian Authority President Mahmoud Abbas, who was criticized by Palestinians when he condemned the Israeli teens' kidnappings, called on Israel on Tuesday to immediately stop its strikes, warning the operation would drag the region into instability.
Abbas said a truce was needed to "spare the innocent from mass destruction."
And a similar call for an end to hostilities came from the Arab League.
Secretary-General Nabil al-Arabi asked for the U.N. Security Council to convene on the matter.
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