JERUSALEM — On a day rattled by a fury of air attacks, Israel and Hamas found themselves Wednesday searching for a way forward, with a senior Israeli military official declaring that a ground invasion of Gaza was a “very high possibility.”

Israel announced it would observe a unilateral “humanitarian truce” for five hours Thursday to allow Gaza residents to stock up on food and other supplies and allow humanitarian aid to reach civilians. The pause in fighting was requested by the United Nations, said army spokesman Lt. Col. Peter Lerner.

It was unclear whether Hamas would also hold its fire. The militant group rejected an earlier cease-fire proposed by Egypt, and a top Hamas leader declared that the Islamist militant group was alone in the world as it battled Israel.

Hamas continued to shower rockets Wednesday into southern and central Israel, including Tel Aviv, underscoring the extent to which the militants believe they still have the military capability to persuade Israel to accept their terms, analysts said.

“From their rationale, they are holding strong, as if they have nothing to lose,” said Miri Eisen, a former Israeli army intelligence official. He added: “If they feel they have nothing to lose, they can continue this for a long time.”

That attitude is bringing increasing pressure on Israel. Hundreds of Israeli airstrikes have killed hundreds of Palestinians but have done little to stop Hamas rockets from striking Israeli towns. Human rights activists are accusing Israel of killing innocent civilians and possibly committing war crimes. Egypt, once a reliable ally, no longer seems to have the negotiating clout it once had.

All this is generating discussions – within Israeli political and military circles and on television, radio and editorial pages – of a possible ground invasion of Gaza in the coming days. In Tel Aviv, a high-ranking Israeli military official told reporters Wednesday, “If you want to efficiently fight terrorism, you need to have boots on the ground.”

More than 113 rockets were fired from Gaza into Israel on Wednesday, according to the Israeli military.

By Wednesday night, 222 people had been killed in Gaza during the nine-day operation, including 49 minors and 24 women, according to the Gaza Health Ministry. More than 1,600 people have been wounded in Gaza, the officials said.

Among the latest casualties were four Palestinian children, all under the age of 12, who were killed by an Israeli missile or shell while playing on a beach in Gaza near a hotel used by foreign journalists, according to witnesses and Palestinian officials. The four boys were cousins. Seven others – adults and children – were reported wounded in the strike.

The Israeli army, calling the incident tragic, said the target had been a Hamas operative.