Gaza militants fired hundreds of rockets into southern Israel on Sunday, killing at least four Israelis and bringing life to a standstill across the region in the bloodiest fighting since a 2014 war.
As Israel pounded Gaza with airstrikes, the Palestinian death toll rose to 22, including two pregnant women and two babies.
The bloodshed marked the first Israeli fatalities from rocket fire since the 2014 war.
With Palestinian militants threatening to send rockets deeper into Israel and Israeli reinforcements massing near the Gaza frontier, the fighting showed no signs of slowing down.
Israeli Prime Minister Benjamin Netanyahu spent most of the day huddled with his Security Cabinet.
Late Sunday, the Cabinet instructed the army to "continue its attacks and to stand by" for further orders.
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Israel also claimed to have killed a Hamas commander involved in transferring Iranian funds to the group. Israel and Hamas, an Islamic militant group that seeks Israel's destruction, have fought three wars since Hamas violently seized control of Gaza from Western-backed Palestinian forces in 2007.
They have fought numerous smaller battles, most recently two rounds in March.
While lulls in fighting used to last for months or even years, these flare-ups have grown increasingly frequent as a desperate Hamas, weakened by a crippling Egyptian-Israeli blockade imposed 12 years ago, seeks to put pressure on Israel to ease the closure.
The blockade has ravaged Gaza's economy, and a year of Hamas-led protests along the Israeli frontier has yielded no tangible benefits.
In March, Hamas faced several days of street protests over the dire conditions. With
"Hamas needs to make its calculus, balancing its hope for improvement against its fear of escalation." In Washington, U.S. Secretary of State Mike Pompeo said Israelis have "every right to defend themselves."
He expressed hope that the recent cease-fire could be restored. The UN Mideast envoy, Nickolay Mladenov, called for a halt in rocket fire and "a return to the understandings of the past few months before it is too late."