17 Dead, Over 100 Hurt as Israel Attacks Gaza and Hamas Shells Haifa, Jerusalem, Tel Aviv

Israeli warplanes killed 15 Palestinians and wounded at least 100 Tuesday, pounding the Gaza Strip in a new campaign to stamp out Hamas rocket fire as the two sides slid toward another major conflict. 

In the most serious flare-up over Gaza since November 2012, it comes as Israel struggles to contain a wave of violence in Arab towns over the grisly murder of a Palestinian teenager by Jewish extremists. 

In the evening, the armed wing of Hamas claimed that it fired several rockets at Jerusalem, Tel Aviv and Haifa.

"For the first time, the (Ezzedine al-) Qassam Brigades strike Haifa with an R160 rocket, and strike occupied Jerusalem with four M75 rockets and Tel Aviv with four M75 rockets," a statement said.

Earlier, three loud explosions rocked Jerusalem shortly after air raid sirens wailed across the city, Agence France Presse correspondents said.

The sirens sounded at about 1900 GMT, with at least four bright flashes lighting the sky southwest of the city, a correspondent said.

The Israeli army had no immediate comment on the attack. Media reports also spoke of sirens sounding north of Tel Aviv for the first time as Hamas militants stepped up their battle against Israel.

Also in the evening, Israeli forces killed four Palestinian militants who landed on a beach in southern Israel a short distance from the Gaza Strip and attacked a military base, the army said.

"A number of terrorists came out of the ocean and attacked the base with Kalashnikov rifles and hand grenades," spokesman Lieutenant Colonel Peter Lerner said.

Soldiers at the base, near the Zikim kibbutz, responded. Ground troops killed two of the attackers, air raids a third and naval forces the fourth, Lerner said.

One soldier was lightly wounded, he added.

The Ezzedine al-Qassam Brigades, the armed wing of the Islamist group Hamas, reported the attack. It said nothing of losses among its own forces but claimed heavy Israeli casualties.

Al-Qassam also said it fired a rocket barrage at two Israeli army bases on Tuesday, shortly after its militants attempted to infiltrate Israel by sea.

It said it fired "10 Katyusha rockets" at the bases, one of which it said was at Zikim, on Israel's southern coast where the infiltration attempt occurred.

Palestinian President Mahmoud Abbas demanded that Israel "immediately stop" its air campaign, dubbed Operation Protective Edge, and asked the world to pressure Prime Minister Benjamin Netanyahu's government.

But Netanyahu was expected to order a "significant broadening" of the operation and instruct the army to "take off the gloves," army radio said, quoting a source close to the premier.

After nearly four weeks of intensifying rocket fire on the south, Israel appeared bent on dealing the Islamist Hamas movement a heavy blow, with the cabinet reportedly authorizing the call up of some 40,000 reservists. 

In central Gaza, one man was killed near Nusseirat refugee camp, medics said. Witnesses said he was a member of Hamas' armed wing, the Ezzedine al-Qassam Brigades.

Shortly afterwards, another four people were killed when a missile slammed into a car in Gaza City, medics said. 

Relatives told Agence France Presse the victims were all Hamas militants. One was identified as Mohammed Shaaban, 32,who ran the Brigades' naval unit.

Seven more people were killed and at least 25 wounded when a missile struck a house in Khan Yunis in southern Gaza, medics said. There was no immediate word on their identities.

Hamas spokesman Sami Abu Zuhri warned Israel was "playing with fire" and would pay for its ongoing operations. 

Later on Tuesday, Abu Zuhri said that "all Israelis" would be targeted after the deadly strike on the Khan Yunis house.

"The Khan Yunis massacre... of children is a horrendous war crime, and all Israelis have now become legitimate targets for the resistance."

Witnesses said a drone launched a warning flare, prompting relatives and neighbors to gather at the house as a human shield, but shortly afterwards an F-16 fired a missile which leveled the building.

Two teenage boys were among those killed, emergency services spokesman Ashraf al-Qudra said.

Shortly afterwards, two Palestinians were killed in an air strike in Shejaiya, east of Gaza City, emergency services spokesman Ashraf al-Qudra told AFP.

A further two separate air strikes killed two people, including a teenager.

One hit a tuktuk (motorized rickshaw) in Beit Lahiya in the north of Gaza, killing a "young man," and one west of Gaza City killed a 16-year-old boy, Qudra said.

Earlier, three people were killed when a missile struck a car in the Daraj neighborhood in the center of Gaza City, he said, correcting an earlier toll of four fatalities.

Hamas' al-Aqsa TV showed gruesome images of charred body parts being loaded onto ambulance stretchers.

The Israeli army was preparing all options to stamp out rocket fire from Gaza, including a ground assault, a senior official told AFP. 

"The army is preparing for all possible scenarios, including an invasion or a ground operation," he said.

Military spokesman General Moti Almoz told the radio "we have been instructed by the political echelon to hit Hamas hard,"  saying the operation would take place "in stages." 

He also confirmed Israel was preparing for a possible ground offensive. 

"All options are on the table; all these steps are being considered. Two brigades, which are currently stationed around the Gaza Strip, are prepared and ready, and in the coming days, more will arrive," he said.

In a related development, Israel's security cabinet authorized the military to call up 40,000 reservists.

"The security cabinet has voted to call up some 40,000 reservists in preparation for a possible ground operation in the Gaza Strip as part of Operation Protective Edge," the Ynet news website said.

Contacted by AFP, Israeli officials refused to comment.

Around Gaza, dozens of tanks and soldiers could be seen massing along the border, AFP correspondents reported. 

Defense Minister Moshe Yaalon warned it was likely to be a protracted campaign. 

"We are preparing for a campaign against Hamas, which will not end in just a few days," he said in a statement which defined the aim as being "to exact a very heavy price from Hamas." 

Since June 12, when the current round of tit-for-tat violence began, more than 250 rockets have hit southern Israel, with another 40 intercepted by the Iron Dome air defense system. 

So far no Israelis have been killed. 

Since midnight, militants have fired more than 100 rockets, an army spokeswoman told AFP, saying only around 33 of them had hit Israeli territory. 

All schools and summer camps were canceled within a 40 kilometer (25 mile) radius of Gaza, except those being held in protected spaces, army radio reported. 

"We have to hit Hamas because our power of deterrence has been reduced," Interior Minister Gideon Saar told public radio. 

"No one is enthusiastic about the idea of a military confrontation, but we cannot hesitate any more. 

"We cannot restore the calm without proving to Hamas that it is absolutely in its interest to halt attacks on Israel, but to do that, we must hit it sufficiently hard."

The rocket fire drew a strong reaction from Washington and Brussels.

"We strongly condemn the continuing rocket fire into Israel, but we also support Israel’s right to defend itself against these attacks," U.S. State Department spokeswoman Jen Psaki said. 

On a visit to the south, EU Ambassador Lars Faaborg Andersen also denounced the ongoing fire, expressing the bloc's "unreserved solidarity" with those living there.

"Indiscriminate shooting of rockets against innocent civilians can never be a legitimate response," he said in remarks broadcast on army radio. 

"It must stop. The situation must be de-escalated."

The latest flare-up comes as Israel arrested six Jewish extremists in connection with the grisly kidnap and murder of the Palestinian teenager, burned alive in a suspected revenge attack the killing of three Israeli youths in the occupied West Bank.

Three of them have confessed, an official told AFP. 

The killing sparked five days of clashes between protesters and riot police in annexed east Jerusalem and Arab towns across Israel.

Police arrested another 39 people overnight, raising the overall number of people detained to 299.