The flare-up was the worst fighting between Israel and Gaza groups since Israel and Hamas fought an 11-day war last year, adding to the destruction and misery that have plagued blockaded Gaza for years.

Since Friday, Israeli aircraft had pummelled targets in Gaza while the Iran-backed Palestinian Islamic Jihad (PIJ) terrorist group fired hundreds of rockets at Israel.?

The terrorist group PIJ originated in the Gaza Strip during the 1970s and it is committed to the creation of an Islamic Palestinian state and the destruction of Israel, according to the non-profit Federation of American Scientists (FAS).

Over three days of fighting, 43 Palestinians were killed, including 15 children and four women, and 311 were wounded, the Palestinian Health Ministry said. Israel said some of the dead were killed by misfired rockets.

Israel on Monday said it was partially reopening crossings into Gaza for humanitarian needs and would fully open them if calm was maintained. Fuel trucks were seen entering a cargo crossing for the first time since crossings with the Gaza Strip were closed last week, prompting a fuel shortage that ground Gaza's lone power plant to a halt on Saturday. The plant was set to resume full operations later on Monday. Gaza suffers from a chronic power crisis.

Life for hundreds of thousands of Israelis was disrupted during the violence. Security precautions imposed in recent days on residents of southern Israel were being gradually lifted Monday, the military said.

Both sides boasted of their successes. Speaking to reporters in Tehran on Sunday, PIJ leader Ziad al-Nakhalah said the group remained strong despite losing two of its leaders. "This is a victory for Islamic Jihad," he said.

Despite that claim, the PIJ undoubtedly sustained a blow during Israel's fierce offensive. Beyond losing the two leaders, it depleted its arsenal by firing hundreds of rockets without striking a single Israeli, thanks to Israel's missile defense system that shot most of them down. Its own rockets may have killed Gazans, according to Israel.

The ceasefire deal contained a promise that Egypt would work for the release of two senior PIJ detainees held by Israel, but there were no guarantees this would happen. The weekend's fighting was also bound to complicate Islamic Jihad's relations with Hamas.

A senior Israeli diplomatic official said the offensive had taken Islamic Jihad's capabilities back "decades". The flareup was "a successful counterterrorism operation" because Israel achieved its goals in a brief period of time, he said, speaking on condition of anonymity because he was not authorised to discuss the operation with the media.

The violence had threatened to spiral into another all-out war but ended up being contained because Gaza's ruling Hamas group stayed on the sidelines, possibly because it fears Israeli reprisals and undoing economic understandings with Israel, including Israeli work permits for thousands of Gaza residents, that bolster its control over the coastal strip.?

Israel and Hamas have fought four wars since the group overran the territory in 2007.?

Israel launched its operation with a strike Friday on a leader of the Islamic Jihad, saying there were "concrete threats" of an anti-tank missile attack against Israelis in response to the arrest last week of another senior Islamic Jihad member in the West Bank. That arrest came after months of Israeli raids in the West Bank to round up suspects following a spate of Palestinian attacks against Israel.?

It killed another Islamic Jihad leader in a strike on Saturday.

Israel said some of the deaths during this round were caused by errant militant rocket fire, including one incident in the Jebaliya refugee camp in northern Gaza in which six Palestinians were killed on Saturday when a projectile hit a home in the same area of Jebaliya, killing two men. Palestinians held Israel responsible, while Israel said it was investigating whether the area was struck by an errant rocket.

In the occupied West Bank on Monday, Israeli troops demolished the homes of two Palestinians suspected of carrying out a deadly attack against Israelis in the city of Elad in May. The soldiers faced a violent protest during the operation, the military said.?

The outburst of violence in Gaza was a key test for Israel's caretaker Prime Minister Yair Lapid, who lacks experience leading military operations. Still, he unleashed the offensive less than three months before a general election in which he is campaigning to keep the job.

US President Joe Biden said he welcomed the cease-fire between Israel and Gaza-based militants.

“Over these last 72-hours, the United States has worked with officials from Israel, the Palestinian Authority, Egypt, Qatar, Jordan, and others throughout the region to encourage a swift resolution to the conflict,” he said in a statement Sunday.?

The UN Security Council was to hold an emergency meeting on Monday on the violence. China, which holds the council presidency this month, scheduled the session in response to a request from the United Arab Emirates, which represents Arab nations on the council, as well as China, France, Ireland and Norway.

“We underscore our commitment to do all we can towards ending the ongoing escalation, ensuring the safety and security of the civilian population, and following-up on the Palestinian prisoners file,” said UN Special Coordinator for the Middle East Peace Process Tor Wennesland in a statement.?

The Israeli army said militants in Gaza fired about 1,100 rockets toward Israel, with about 200 of them landing inside the Palestinian enclave. The army said its air defences had intercepted 380 of them, including two fired toward Jerusalem. The military did not specify what happened to the remainder, but they likely fell in open areas or broke up in the air.?

Islamic Jihad has fewer fighters and supporters than Hamas, and little is known about its arsenal. Both groups call for Israel's destruction, but have different priorities, with Hamas constrained by the demands of governing.

Hamas had a strong incentive to avoid another war. Last year's Israel-Hamas war, one of four major conflicts, and several smaller battles over the last 15 years, have exacted a staggering toll on the impoverished territory's 2.3 million Palestinian residents.

Over the past year, Israel and Hamas have reached tacit understandings based on trading calm for work permits and a slight easing of the border blockade, imposed by Israel and Egypt when Hamas overran the territory 15 years ago. Israel has issued 12,000 work permits to Gaza labourers, and has held out the prospect of granting another 2,000 permits.

(With AP inputs)