JERUSALEM — Israel launched a fierce air and sea offensive across the Gaza Strip on Tuesday following a wave of rocket launches by the militant group Hamas, pounding targets across the coastal enclave in a barrage that killed 23 people and injured more than 100, Palestinian health officials said.
Air raid sirens sounded in Jerusalem and Tel Aviv as volleys of rockets sailed into Israel. Israeli soldiers killed five Palestinian gunmen who landed from the sea on Israel’s southern coast. Both sides threatened to step up their assaults.
Hostilities have flared across the Gaza border since the kidnapping and killing last month of three Israeli teenagers in the West Bank, which Israel blamed on Hamas. After Egyptian attempts to broker a cease-fire failed, the cross-border fighting intensified.
The Israeli security cabinet approved the call-up of 40,000 reservists as troops and tanks were mobilized around the Gaza Strip, signaling a readiness to launch a ground operation.
But analysts said the move was intended as a threat to back up a calibrated escalation designed to press Hamas to halt rocket fire while avoiding getting bogged down in a costly ground war.
In a televised statement to the nation, Prime Minister Benjamin Netanyahu said he had ordered a “significant broadening” of army operations in Gaza, and he urged Israelis to be patient, “because this operation may take time.”
The army said it had hit 270 targets across the Gaza Strip, including the homes of Hamas operatives, concealed rocket launchers, tunnels, weapons depots and training bases.
A spokesman for the Qassam Brigades, the armed wing of Hamas, warned Tuesday night that if Israel continued to bomb houses in Gaza, the group would “broaden the range of targeting,” striking deeper into Israel.
Less than two hours later, a barrage of dozens of long-range rockets was fired at cities and towns in central and southern Israel. Three landed near Jerusalem and two were intercepted over Tel Aviv. Public bomb shelters were opened in both cities. One rocket reached Hadera, north of Tel Aviv, more than 70 miles from Gaza.
In a seaborne raid in southern Israel, a group of five Hamas gunmen armed with grenades tried to infiltrate an Israeli army base at Zikim, close to the Gaza border. An army spokesman said that after the group was spotted by a lookout, the militants were killed in a firefight with troops who rushed to the scene.
In another incident, explosives detonated in a tunnel near Kerem Shalom on the Gaza border, but no casualties were reported, the military said.
In the deadliest air attack in the Gaza Strip, Palestinians said seven people were killed and more than two dozen wounded, including women and children, when a house belonging to the Kawara family was struck in the city of Khan Yunis.
According to a report on local television, people had gathered on the roof of the house to serve as human shields after Israel fired a small warning rocket at the building, but it was bombarded anyway. The Israeli army said it was checking the report.
In another strike on a house, six members of the Hamad family were killed in the town of Beit Hanoun in the northern Gaza Strip, local media reported.
A senior operative in Hamas’ naval commando unit was killed with at least two other people when rockets struck his car, the army and Palestinians said, and another militant was reportedly killed when his house was bombed.
More than 150 rockets and mortar rounds were launched at Israel, most of them landing in open areas, while 29 rockets aimed at populated areas were intercepted by Israel’s Iron Dome missile defense system, the military said.
Residents of Israeli towns within a 25-mile radius of Gaza were ordered to stay close to safe rooms, summer camp activities were suspended and large gatherings were forbidden as a precaution against the continuing rocket fire.
Analysts said that while neither Israel nor Hamas had wanted a full-blown confrontation, events on the ground were creating a dynamic of their own.
Netanyahu had been pressed by hard-line partners in his governing coalition, and by hawkish members of his own party, to respond forcefully to the continuing rocket attacks from Gaza. And Hamas, politically isolated and facing stepped-up airstrikes from Israel, could not be seen to be standing by, experts said.
Hamas has been weakened by the removal of its patron, the Muslim Brotherhood, from power in Egypt, and a reconciliation accord with the Fatah movement of Palestinian President Mahmoud Abbas has failed to produce real power-sharing, analysts said.
“Hamas is in dire straits, and it has nothing to lose from an escalation with Israel,” said Mkhaimar Abusada, a professor of political science at Al-Azar University in Gaza City. “They are calculating that any escalation can get Hamas out of the impasse and raise their popularity, showing that they are still committed to resistance and fighting Israeli occupation.”
Hamas’ military wing, rather than the political leadership, was calling the shots now, Abusada said. “We all know that the Qassam Brigades are the ones in control of Hamas.”