GAZA -- Israel on Wednesday launched one of the most ferocious assaults on Gaza since its invasion four years ago, hitting at least 20 targets in aerial attacks that killed the top military commander of Hamas, drew strong condemnation from Egypt and escalated the risks of a new war in the Middle East.
The Israelis coupled the intensity of the airstrikes with the threat of another ground invasion and warnings to all Hamas leaders in Gaza to stay out of sight or risk the same fate as the Hamas military commander, Ahmed al-Jabari, who was killed in a pinpoint airstrike as he was traveling by car down a Gaza street. "We recommend that no Hamas operatives, whether low level or senior leaders, show their faces above ground in the days ahead," the Israel Defense Forces said in a Twitter message.
The ferocity of the airstrikes, which Israel called Operation "Pillar of Defense" in response to repeated rocket attacks by Gaza-based Palestinian militants, provoked rage in Gaza, where Hamas said the airstrikes amounted to war and promised a harsh response. It quickly launched dozens of rockets into southern Israel, including several that struck the city of Beersheba, shattering windows and damaging cars but causing no injuries.
Civil-defense authorities in Israel, anticipating retaliation, raised alert levels early in the day and told residents in southern Israel to take precautions. Many remained indoors or congregated in bomb shelters.
The Hamas-run Health Ministry in Gaza said the Israeli attacks had killed at least five others besides Mr. Jabari, including a baby and a 7-year-old girl, and had wounded at least 40.
The abrupt escalation in hostilities between Israel and Hamas, the militant organization regarded by Israel as a terrorist group sworn to Israel's destruction, came amid rising tensions between Israel and all of its Arab neighbors. Israel has faced growing lawlessness on its border with the Sinai, including cross-border attacks. It recently fired twice into Syria, which is caught in a civil war, after munitions fell in the Israeli-occupied Golan Heights, and it has absorbed rocket fire from Gaza, which has damaged homes and frightened the population.
Israeli officials had promised a robust response to the rocket fire, but for the moment, at least, opted against a ground invasion and instead chose airstrikes and targeted killings.
The Israeli attacks especially threatened to further complicate Israel's fragile relations with Egypt, where the Islamist-led government of President Mohamed Morsi, reversing a policy of ousted predecessor Hosni Mubarak, had established closer ties with Hamas and had been acting as a mediator to restore calm between Israel and Gaza-based militant groups.
In the first crisis in Israeli-Egyptian relations since Mr. Morsi came to power, he called the Israeli actions "wanton aggression on the Gaza Strip." He ordered Egypt's ambassador to Israel to return home, summoned the Israeli ambassador to protest, and called for emergency meetings of both the United Nations Security Council and the Arab League over the Gaza attacks. Egyptian state media said Foreign Minister Mohamed Amr had "warned Israel against the consequences of escalation and the negative reflections it may have on the security and stability of the region."
Mr. Morsi's Freedom and Justice Party, which was founded by the Muslim Brotherhood, posted a video on its Web site of what was described as the burned body of a Palestinian child said to have been killed in the Israeli attacks, in what appeared to be a deliberate attempt to inflame passions. His party also issued a statement saying: "The wanton aggression against Gaza proves that Israel has yet to realize that Egypt has changed and that the Egyptian people who revolted against oppression will not accept assaulting Gaza."
A spokesman for Hamas, Fawzi Barhoum, said the Israelis had "committed a dangerous crime and broke all redlines," and that "the Israeli occupation will regret and pay a high price."
Military officials in Israel, which announced responsibility for the death of Mr. Jabari, later said in a statement that their forces had carried out additional airstrikes in Gaza targeting what they described as "a significant number of long-range rocket sites" owned by Hamas that had stored rockets capable of reaching 25 miles into Israel. The statement said the airstrikes had dealt a "significant blow to the terror organization's underground rocket-launching capabilities."
Yisrael Katz, a minister from Israel's governing Likud Party, issued a statement saying that the operation had sent a message to the Hamas political leaders in Gaza "that the head of the snake must be smashed. Israel will continue to kill and target anyone who is involved in the rocket attacks."Hamas and medical officials in Gaza said both Mr. Jabari and a companion were killed by the airstrike on his car in Gaza City. Israeli news media said the companion was Mr. Jabari's son, but there was no immediate confirmation.
The Israel Defense Forces said in a statement that Mr. Jabari had been targeted because he "served in the upper echelon of the Hamas command and was directly responsible for executing terror attacks against the state of Israel in the past number of years," including the 2006 abduction and five-year incarceration of Gilad Shalit, an Israeli soldier, on the Israel-Gaza border.
The statement said the purpose of the attack was to "severely impair the command and control chain of the Hamas leadership as well as its terrorist infrastructure."
The statement did not specify how the Israelis knew Mr. Jabari was in the car but said the operation had been "implemented on the basis of concrete intelligence and using advanced capabilities."
A video released by the Israel Defense Forces and posted on YouTube showed an aerial view of the attack on what it identified as Mr. Jabari's car on a Gaza street as it was targeted and instantly blown up in a pinpoint bombing. News photographs of the aftermath showed the car's blackened hulk surrounded by a large crowd.
The Israel Defense Forces later posted a Twitter showing a mug shot of Mr. Jabari overwritten by the word "eliminated."
Hamas has controlled Gaza since 2007, two years after the Israelis withdrew from the territory captured in the 1967 Arab-Israeli war. But Israeli forces went back into Gaza in the winter of 2008-09 in response to what they called a terrorist campaign by Palestinian militants there to launch rockets into Israel. The three-week military campaign killed as many as 1,400 Palestinians, including hundreds of civilians, and was widely condemned internationally.
Since then Hamas has mostly adhered to an informal, if shaky, cease-fire and at times tried to enforce the smaller militant groups to stick to it. But in recent months, under pressure from some of the Gaza population for not avenging deadly Israeli airstrikes, it has claimed responsibility for participating in the firing of rockets. Last week, it also claimed credit for detonating a tunnel packed with explosives along the Israel-Gaza border while Israeli soldiers were working nearby.
Israel has mainly responded to rocket attacks in recent years by attacking the rocket-launching squads, empty training sites or weapons manufacturing plants. Israel also had not attempted any high-profile assassinations, although it has killed some local leaders of small, radical Islamic organizations that it said were involved in planning attacks on Israelis.
Israel has long said it would hold Hamas responsible for attacks launched from Gaza on its forces and population, regardless of which group was behind them. Like the United States and Europe, Israel defines Hamas as a terrorist organization. Hamas has not recognized Israel's right to exist.
Mr. Jabari became the acting leader of the Hamas military wing after Israel had severely wounded Muhammad Deif, the top commander, in an assassination attempt in 2003. Mr. Jabari had survived several previous Israeli raids. In 2004, Israeli planes attacked his house killing one of his sons and three other relatives.
Shin Bet, the Israeli security agency, considered Mr. Jabari responsible for what it called "all anti-Israeli terror activity" emanating from Gaza.
He was also known for having played a major role in negotiations that led to the release of Mr. Shalitlast year. Mr. Jabari personally escorted Mr. Shalit during a handover to Egyptian intermediaries as part of a prisoner exchange for hundreds of Palestinians held in Israeli jails. Video of the handoff to Egypt showed Mr. Jabari standing near Mr. Shalit.
Lt. Col. Avital Leibovich, a spokeswoman for the Israeli military, acknowledged Mr. Jabari's role in that prisoner exchange during a conference call with journalists on Wednesday announcing the airstrike on Mr. Jabari's car. She also said Mr. Jabari had "a lot of blood on his hands."
Fares Akram reported from Gaza, and Isabel Kershner from Jerusalem. Reporting was contributed by Mayy El Sheikh and David D. Kirkpatrick from Cairo, Gabby Sobelman in Jerusalem, Rina Castelnuovo in Beersheba, Israel, and Rick Gladstone from New York.
This article originally appeared in The New York Times.