The Israeli military has intensified its assault on Gaza, as Palestinian militants continue to fire rockets into Israel on the fifth day of hostilities.
Israel’s army said air and ground forces were involved in attacks on Friday but had not entered Gaza.
Video from Gaza City showed the night sky lit up by explosions from Israeli artillery, gunboats and airstrikes.
More than 100 people have been killed in Gaza and seven in Israel since fighting began on Monday.
Meanwhile, Jewish and Israeli-Arab mobs have been fighting within Israel, prompting its president to warn of civil war.
Defence Minister Benny Gantz ordered a “massive reinforcement” of security forces to suppress the internal unrest that has seen more than 400 people arrested.
Police said Israeli Arabs have been responsible for most of the trouble and reject the accusation that they are standing by while gangs of Jewish youths target Arab homes.
Israeli Prime Minister Benjamin Netanyahu has proposed introducing “administrative detention” for rioters. The controversial measure would allow authorities to detain people for extended periods of time without charge.
In Gaza, Palestinians fearing an incursion by Israeli troops have been fleeing areas close to the border with Israel. The Israeli military said it had conducted an operation overnight to destroy a network of Hamas tunnels, but no troops had entered Gaza.
Meanwhile, Hamas fired three more volleys amounting to about 55 rockets in total into Israel on Thursday evening. An 87-year-old woman died after falling on her way to a bomb shelter near Ashdod in southern Israel. Other areas including Ashkelon, Beersheba and Yavne were also targeted.
On Thursday, Israel’s military called up 7,000 army reservists and deployed troops and tanks near its border with Gaza. It said a ground offensive into Gaza was one option being considered but a decision had yet to be made.
In a statement released early on Friday morning, Mr Netanyahu said the Israeli military operation against Palestinian militants in Gaza would continue for as long as necessary. He said Hamas, the Islamist group that rules Gaza, would pay a heavy price.
A Hamas military spokesman said the group was ready to teach Israel’s military “harsh lessons” should it decide to go ahead with a ground incursion.
His plea echoed that of other diplomats – including from Israel’s ally the US – but appeals to Israeli and Palestinian leaders have so far failed to produce a ceasefire agreement.
A senior Hamas official has said the group is ready for a “reciprocal” ceasefire if the international community pressures Israel to “suppress military actions” at the disputed al-Aqsa Mosque in Jerusalem.
At least 103 Palestinians have been killed since Monday, including 27 children, and more than 580 wounded, the health ministry in Gaza said. Officials in the territory said many civilians had died.
Israel says dozens of those killed in Gaza were militants, and that some of the deaths are from misfired rockets from Gaza.