JERUSALEM — Israeli warplanes launched a large-scale attack across the Gaza Strip on Friday, one of the fiercest in years, after a Palestinian sniper killed an Israeli soldier along the border fence during a day of escalating hostilities.

Successive explosions rocked Gaza City at nightfall and the streets emptied as warplanes struck dozens of 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 analysts said neither side seemed eager to have an all-out conflict.

Indeed, after 1 a.m., about seven hours into the Israeli assault, a Hamas spokesman announced that the cease-fire had been restored with the mediation of Egypt and the United Nations. There was no immediate confirmation of a renewed truce from the Israeli side.