JERUSALEM — Israel and its Palestinian adversaries in Gaza sharply escalated the latest resurgence of hostilities Tuesday, with the Israeli military conducting a deadly aerial bombardment that targeted at least 160 Gazan sites, including homes, and militants in the enclave responding with missile volleys aimed at Israeli population centers, including Tel Aviv and Jerusalem.
The Israeli military said Palestinian militants in Gaza fired more than 160 rockets and that Israel's missile defense system had thwarted at least 23 of them. More than 100 landed in Israel, the military said, but it was unclear whether they had caused any casualties or damage.
Hamas, the militant group that controls Gaza, took responsibility late Tuesday for firing up to 40 long-range rockets, some of them intercepted over Tel Aviv and Jerusalem, where sirens sounded around 10 p.m. Hamas also claimed to have launched a rocket toward the northern Israeli city of Haifa, 88 miles away, which if confirmed would be the farthest range yet of the Gaza-based weapons.
Palestinian witnesses and health officials said at least 15 people had been killed in the Israeli attacks, including seven in a house that was bombed after its occupants had been warned in a phone call to leave.
It was the deadliest day so far in the latest escalation of the long-running Israeli-Palestinian conflict, fed partly by the raw rage over the kidnapping and killing of three Israeli teenagers in the occupied West Bank last month, a massive security crackdown by Israel there and the grisly kidnapping and killing of a Palestinian teenager from East Jerusalem last week.
In an ominous indication of further escalation, the Israeli government approved the call-up of 1,500 reservists, mainly Home Front Command and aerial defense units, and said later Tuesday that it had authorized the military to mobilize as many as 40,000 additional reservists if necessary for a possible ground invasion.
The Israeli military also reported Tuesday, with little detail, that it had defeated an effort to attack an army base in southern Israel by "several gunmen armed with grenades" who had approached from the sea. The army said it had killed four of the gunmen and was searching for others.
The Israeli aerial barrage followed Monday's firing of about 80 rockets out of Gaza that reached deep into southern Israel.
Witnesses and Health Ministry officials in Gaza said the first of at least five deadly Israeli airstrikes Tuesday destroyed a car in Gaza City, killing three unidentified occupants. The second was an Israeli bomb or rocket that witnesses said had been fired by an F-16 warplane on a house in Khan Younis, a town in the southeast part of Gaza, where seven occupants were found dead in the wreckage.
A telephoned warning was made to the owner of the targeted home in Khan Younis five minutes before the bombing, apparently part of the Israeli military's stated effort to minimize unintended civilian casualties. Salah Kaware, 25, who lived in the house, said that a call came to the cellphone of his brother's wife, and that the caller urged them to leave.
An unidentified member of Hamas was reportedly killed in a third airstrike, in an open space in central Gaza. Health officials in Gaza said at least four residents had been killed in Israeli strikes elsewhere, including Gaza City and the northern part of Gaza. Ashraf al-Qedra, a Health Ministry spokesman, said more than 90 people had been wounded since the Israeli air assaults had begun.
The Israeli military said that its targets had included what it called a "terror command center embedded within civilian infrastructure" utilized by a militant in the southern Gaza town of Rafah.
The air campaign comes after three weeks of escalating confrontation, with rocket attacks from Gaza against southern Israel, and Israeli airstrikes on targets it has described as concealed rocket launchers, training sites and weapons manufacturing facilities associated with Hamas and other militant groups. Fury on both sides over the teenage victims of Israel-Palestinian enmity have fed the momentum.
Hamas' military wing said in an emailed statement that the bombing of the houses was "a serious escalation" that "will oblige us to enlarge our attacks deeper into Israel."
Early Tuesday, the Israel Defense Forces announced on Twitter that it had "commenced Operation Protective Edge in Gaza against Hamas in order to stop the terror Israel's citizens face on a daily basis."
In a statement from his office, the Israeli defense minister, Moshe Yaalon, said, "Hamas is leading this current confrontation to a place in which it aspires to exact a heavy price from our home front."
"In the last few hours we have attacked with force and struck dozens of Hamas' assets," Yaalon added, saying that the military was "continuing its offensive effort in a manner that will exact a very heavy price from Hamas." He said the campaign was likely to last more than a few days.
In a conference call with reporters, Lt. Col. Peter Lerner, a spokesman for the Israeli military, said there would be "a gradual increase in the pressure we are putting on Hamas."
Lerner said that Israel was "watching to see what the reaction is with Hamas, to see how they respond to our steps." His comments echoed those of other officials and experts, who have suggested that the initial blitz was meant as a warning, with the hope that Hamas would rein in its fire to avoid a ground invasion. Referring to such a development, Lerner said, "I don't see that happening immediately."