JERUSALEM — Israeli warplanes launched a wide-scale attack across the Gaza Strip on Friday, one of the fiercest in years, punctuating a day of escalating hostilities in which a Palestinian sniper killed an Israeli soldier along the border fence.
Successive explosions rocked Gaza City at nightfall and the streets emptied as warplanes struck sites that Israel said belonged to the military wing of Hamas, the Islamist group that controls Gaza.
Israeli security experts said the aerial assault was one of the most intense since a cease-fire ended 50 days of fighting in the territory in 2014. The ferocity of the bombings raised fears that the hostilities could spiral into a war, though by early Saturday morning Hamas said it would revert to the cease-fire.
Prime Minister Benjamin Netanyahu of Israel and his defense minister, Avigdor Lieberman, arrived at military headquarters in Tel Aviv on Friday night for emergency meetings with top officials, a highly unusual event for the start of Sabbath.
At least four Palestinians were killed by initial Israeli gun and tank fire and in the subsequent airstrikes. The military wing of Hamas said that three of the four were members of Hamas.
On the Israeli side of the border, the authorities instructed residents to remain close to bomb shelters as they braced for retaliatory rocket fire from Gaza. The military this week placed batteries of its Iron Dome anti-rocket missile defense system in several locations in central Israel.
Brig. Gen. Ronen Manelis, the chief spokesman for the Israeli military, blamed Hamas for escalating tensions over the past three and a half months, since the beginning of the Hamas-orchestrated mass protests along the border fence. He said the response to Friday’s killing of the soldier along the fence — the first Israeli fatality in the Gaza border area in four years — would be “very severe.”
Speaking on Israeli television after 8 p.m., General Manelis said the Israeli air assault would continue for several hours.
“We’re prepared for a broad array of scenarios and possibilities,” he said, adding, “We are determined to restore security and the sense of security to the Gaza periphery.”
This latest flare-up comes after months of tensions fanned by the often-violent protests along the fence dividing Israel and Gaza, during which Israeli snipers have killed more than 140 mostly unarmed Palestinians, according to Gaza health officials. The military says it has been acting to prevent breaches of the fence and to fend off attacks by Gaza militants, like the one that occurred on Friday.
The protests have since evolved into escalating exchanges of Palestinian mortar and rocket fire against Israeli positions and civilian border communities, and waves of Israeli airstrikes against Hamas targets in Gaza.
Israelis’ nerves have also been frayed by a plague of wildfires set by flaming kites and balloons launched from Gaza into southern Israel, which have charred large tracts of woodland and farmland. One flaming balloon landed in the yard of an Israeli kindergarten this week. It caused no damage or injuries.
Nevertheless, there has been increasing talk of war in recent days, with Israeli leaders warning Hamas that they would not tolerate a continuation of the arson attacks.
The friction had already led to two intense bursts of conflict, which ended with hurried efforts by Egypt to restore the cease-fire. In one such episode last weekend, two Palestinian youths were killed in an Israeli airstrike on an otherwise empty shell of a building used by Hamas as a training site, and four Israelis were wounded as more than 100 mortar shells and rockets were launched from Gaza.
A spokesman for Hamas, Fawzi Barhoum, said on Friday that the marches on the border would continue. Israel and Egypt tightly control the movement of people and goods in and out of Gaza, citing security concerns. Mr. Barhoum said the protests were aimed at breaking the blockade.
“Our people won’t be broken,” he said, “no matter what the sacrifices.”
Iyad Abuheweila and Ibrahim El-Mughraby contributed reporting from Gaza City.