JERUSALEM — A cease-fire ending three days of fierce cross-border fighting between Israel and a Palestinian militant group in Gaza appeared to be holding on Monday, and life on both sides of the lines began to return to normal.

The Israeli military opened an offensive on Friday afternoon with missile strikes aimed against targets of the group, Palestinian Islamic Jihad, saying the action was intended to thwart an imminent attack. It pounded targets in the Gaza Strip from the air, land and sea. Islamic Jihad fired about 1,100 rockets and mortar shells toward Israeli territory, the military said.

Both sides agreed to an Egyptian-mediated cease-fire Sunday night to halt the most intense round of Israeli-Palestinian fighting in more than a year. According to the Ministry of Health in Gaza, at least 44 Palestinians were killed in the fighting, 15 of them children, and 360 people were injured, with 20 of them in serious condition.

After about a week of closure, Israel reopened Gaza’s border crossings for humanitarian supplies on Monday morning, starting with fuel deliveries to address dire electricity shortages in the enclave. By midday, the Israeli authorities had removed all safety restrictions that had been imposed on residents in the border areas over the past week to keep them close to bomb shelters and out of range of militant sniper fire.

Here is what we know about the consequences of the three-day conflict.

Summing up its campaign in Gaza, the Israeli military said on Monday that it had hit 170 Islamic Jihad targets, eliminating senior commanders of the group as well as rocket launching squads, and destroying launch pits, command posts and weapons stores.

Islamic Jihad said it had lost 12 of its leaders and members. Among them were Taysir al-Jabari, the commander for the northern region of Gaza, and Khaled Mansour, the southern region commander.

Although Islamic Jihad claimed to have gained some vague concessions relating to its prisoners in Israel under the terms of the cease-fire, Israel denied that it had agreed to any conditions other than a cessation of fighting on both sides.

The Israeli military said about 200 of Islamic Jihad’s rockets fell short and landed inside the Gaza Strip, causing casualties among civilians, including children.

And it said that its Iron Dome antimissile defense system carried out 380 interceptions of rockets heading for population centers in Israel, with a success rate of about 96 percent — up from about 90 percent in previous rounds. Tzipi Livni, a former senior Israeli government minister and a veteran negotiator with the Palestinians, said those defenses shortened the duration of the fighting and prevented more casualties.

But the secretary-general of Palestinian Islamic Jihad, Ziad al-Nakhala, also claimed victory shortly after the cease-fire announcement on Sunday night.

“The jihad movement is today stronger, and all the enemy’s cities were within the range of the resistance’s missiles,” he said in a televised speech, adding, “We remained in control of the field despite the power imbalance with the enemy.”

Israel’s interim prime minister burnished his security credentials.

The latest Gaza operation has been widely seen as a success in Israel, with no Israeli deaths and little damage on the Israeli side.

That is playing well for Yair Lapid, the new, centrist prime minister of Israel’s caretaker government, who is running for office in an election scheduled for Nov. 1.

Mr. Lapid has long been accused by critics in Israel of lacking the necessary national security know-how to lead the country in times of war, particularly when compared with his main rival, Benjamin Netanyahu, who has built up a wealth of experience as Israel’s longest-serving prime minister and now leads the opposition.

But by initiating the airstrikes on Friday, Mr. Lapid improved his starting position in the political race, analysts said. And on Sunday, he scored a public relations coup when Mr. Netanyahu, who has refused to attend security briefings with Mr. Lapid in the past, was photographed sitting across the table from him receiving a formal update on the security situation and issued a statement backing the government.

“Now Lapid has gained the image of a prime minister who has led a military operation,” said Gayil Talshir, a political scientist at the Hebrew University of Jerusalem.

Hamas, the main militant group in Gaza, stayed out of the conflict.

Hamas, the largest and most powerful militant group in the blockaded Palestinian coastal enclave of Gaza, sat out the latest conflict with Israel, leaving all the fighting to the smaller Islamic Jihad. The two groups are rivals but often partner in taking on Israel.

Israeli officials and experts said Hamas’s decision to stay on the sidelines, even as the death toll rose in Gaza, was testament to the success of an Israeli government shift in policy toward the impoverished enclave over the last year.

In an effort to improve the economy of Gaza, with a population of about two million and an unemployment rate of about 50 percent, Israel has offered work permits to 14,000 residents of the territory — a small number in relative terms but by far the most since Hamas seized power in 2007, providing a financial lifeline to thousands of families.

Israel says it might expand the number of permits further, to 20,000, depending on the security situation, and that it has also worked over the past year to increase Gaza’s imports and exports.

But the prospects of much greater economic development are hampered by the refusal of Hamas to release the remains of two Israeli soldiers, held since 2014, and its yearslong imprisonment of two Israeli civilians suffering from mental health issues.

Another factor limiting Gaza’s development, Israeli officials say, is that Hamas refuses to recognize Israel’s right to exist and continues to focus on building its military force at the expense of investment in the civilian population.

Islamic Jihad, for its part, denies that Hamas’s decision to stay on the sidelines of this round of fighting has deepened the split between the two groups. Mr. al-Nakhala, the Islamic Jihad leader, said: “Hamas is the backbone of the resistance and we are in a continuous alliance with them to confront the enemy.”

Islamic Jihad failed to link up the West Bank and Gaza.

The secretary-general of Palestinian Islamic Jihad, Mr. al-Nakhala, said his organization wanted to protect the life of Bassem Saadi, a senior Islamic Jihad figure who was arrested by Israeli special forces in the occupied West Bank last week. The militants had threatened reprisals in response to the arrest. Islamic Jihad later demanded his release as part of the Egyptian-mediated cease-fire talks — so far to no avail.

The last two days of conflict in Gaza can be linked back to a spike in violence across Israel and the West Bank several months ago. A spate of Palestinian attacks on civilians in Israel in April and May led to an increase in Israeli raids across the West Bank and almost nightly arrests, culminating in the arrest of Mr. Saadi.

With its threats of retaliation, Islamic Jihad had hoped to curb Israeli actions against the group in the West Bank. But the raids in the West Bank have continued, even as the fighting raged in Gaza.

On Saturday, the Israeli military said it had apprehended 19 suspects belonging to Islamic Jihad in overnight raids across the West Bank. On Sunday it said it had detained another 20.

Israel said it received international support, and avoided criticism from some new Arab allies.

The latest round of violence came soon after a mid-July visit to the region by President Joe Biden. In a statement issued by the White House welcoming the cease-fire late Sunday, Mr. Biden said, “My support for Israel’s security is longstanding and unwavering — including its right to defend itself against attacks.”

Mr. Biden particularly thanked the Egyptian leadership for its central role in bringing the hostilities to an end, as well as Qatar for its help, and said the United States had also worked with officials from Israel, the West Bank-based Palestinian Authority and Jordan.

Israeli officials said strong expressions of support had also come from European countries.

The fighting also highlighted the growing acceptance of Israel in other parts of the Arab world. Past Gaza wars have drawn heavy criticism from other Arab countries. This time, the response was more muted.

Two of the three Arab countries that formalized ties with Israel in 2020 in a process known as the Abraham Accords, Morocco and the United Arab Emirates, expressed concern about the violence but avoided criticism of Israel. Only the third country, Bahrain, directly condemned Israel’s strikes.

Hiba Yazbek, Fady Hanona and Iyad Abuheweila contributed reporting.