Israel launched an aerial offensive in the Gaza Strip on Tuesday, bombing more than 30 targets including homes and calling it part of a campaign named "Operation Protective Edge" targeting Hamas Islamist militants firing rockets at the Jewish state.
The military urged Israelis within a 40-km (24-mile) radius of the southern coastal territory to stay within reach of protected areas and ordered summer camps shut as a precaution against rocket fire.
Palestinian officials said Israel bombed more than 30 targets in little more than an hour before dawn, including two homes in southern Gaza, one of which was identified by a neighbour as belonging to a Hamas member.
Nine people suffered shrapnel injuries. There were no other reported casualties as the buildings were believed to have been evacuated beforehand.
Witnesses said a house bombed in Khan Younis was flattened. The Palestinian Health Ministry said nine neighbours were wounded by debris from that strike.
The Palestinian Interior Ministry said the family in the targeted home had received a telephone call from an Israeli intelligence officer asking them to leave the house because it would be bombed, and the family evacuated in time.
A military spokeswoman confirmed air strikes were launched but had no details.
Military spokesman Lieutenant Colonel Peter Lerner said in a tweet that "Operation Protective Edge is under way, targeting Hamas capabilities that are terrorizing Israel."
Hamas' armed wing threatened an "earthquake" in response to Israel's attacks, and said it had fired a rocket at a southern Israeli town.
In a statement the group denounced Israel's bombing of houses as "exceeding all red lines" and threatened to shoot rockets at longer distances. "We will respond by broadening the range of our targets," the militants said.
Lerner said Gaza militants had fired more than 80 rockets at Israel on Monday, and military officials said more than 200 rockets have been shot at Israel in the past month, an enormous uptick in shootings.
SECURITY CABINET DECIDES
Prime Minister Benjamin Netanyahu's security cabinet decided on Monday to step up air strikes against militants in coastal Gaza. Political sources said ministers stopped short of ordering a ground offensive for now.
Netanyahu had earlier pledged "to do whatever is necessary" to restore quiet to southern Israeli communities though he cautioned against any rush toward wider confrontation with Hamas, whose arsenal includes long-range rockets that can reach Israel's heartland and its business capital Tel Aviv.
But far-right cabinet ministers pressed for a firmer response to silence rocket fire. Foreign Minister Avigdor Lieberman quit an alliance with Netanyahu's party citing dissatisfaction with Netanyahu's policy on Gaza.
The surge in violence has raged since the kidnapping and killing of three Israeli youths last month in the occupied West Bank and a Palestinian teen last week, in an attack for which Israel has arrested six Jewish suspects.
Air raid sirens wailed as far north as the outskirts of Tel Aviv and Jerusalem on Monday night. Israeli police said those were false alarms, but the military said rockets had triggered alerts as far as 80 km (48 miles), the farthest of the latest crisis.
Two Israelis were injured in Monday's rocket strikes.
Lerner told reporters on Monday that Israel had called up several hundred reservists and was prepared to mobilise a total of 1,500. He said the intensity of Hamas rocket fire meant "the Israeli military is talking about preparedness for an escalation."
Hamas claimed responsibility for firing rockets at Israel on Monday for the first time since a 2012 war with Israel that ended in an Egyptian-brokered truce.
The group's death toll on Monday had also been the highest Hamas suffered since the 2012 fighting.
Hamas spokesman Sami Abu Zuhri accused Israel of committing a "grave escalation" in violence and threatened to retaliate, saying Israel would "pay the price."