Mr. Netanyahu ordered a resumption of attacks after Hamas struck two military targets inside Israel on Monday, lobbing a mortar that killed four soldiers at a makeshift base 4 miles from the Gaza border and popping up from a cross-border tunnel to open fire on a military patrol. The military said it killed five militants in a firefight at the tunnel opening.
Hamas responded defiantly to Mr. Netanyahu's comments.
"His threats do not scare Hamas or the Palestinian people," said Samy Abu Zohry, a spokesman for the Islamist group that governs Gaza. "The [Israeli] occupation will pay the price for the massacres against civilians and children."
U.N. Secretary-General Ban Ki-moon singled out Israel, accusing it of "pummeling" Gazans with "indiscriminate destruction" and warned the Jewish state to fulfill its obligations as "an occupying power" to protect civilians.