GAZA CITY - Israeli strikes on Gaza Tuesday killed 15 people and wounded around 100, the emergency services said, as the military began an aerial campaign against militants in the Strip. In the worst strike, a missile slammed into a house in the southern city of Khan Yunis after people had reportedly formed a human shield to protect it, killing seven people. Emergency services spokesman Ashraf al-Qudra told AFP two teenagers were among the dead and that another 25 people were wounded. Witnesses said an Israeli drone fired a warning flare, prompting relatives and neighbours to gather at the house as a human shield and that, shortly afterwards, an F-16 warplane fired a missile that levelled the building. In response, Hamas said ‘all Israelis’ would be potential targets for retaliation. ‘The Khan Yunis massacre... of children is a horrendous war crime, and all Israelis have now become legitimate targets for the resistance,’ spokesman Sami Abu Zuhri said on Facebook. Shortly afterwards, two Palestinians were killed in an air strike in Shejaiya, east of Gaza City, Qudra said without elaborating.The blast shook buildings in the city, and Hamas-run Al-Aqsa TV replayed what it said was a video of the strike, which sent a tall cloud of debris rising into the air. A further two separate air strikes killed two people, including a teenager. One hit a tuktuk (motorised 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.Palestinian president Mahmud 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.The Arab League called Tuesday for the UN Security Council to hold an urgent meeting to discuss the deadly Israeli air campaign against Gaza, Secretary General Nabil al-Arabi said.Fourteen people were killed Tuesday and dozens wounded in a number of attacks in the most serious flare-up in and around the Palestinian territory since November 2012. An official from the pan-Arab bloc told AFP Arabi had “instructed the Arab League’s UN representative to initiate urgent consultations within the Arab group calling for an emergency security meeting of the Security Council.” After nearly four weeks of intensifying rocket fire on the south, Israel appeared bent on dealing the Hamas movement a heavy blow, with the cabinet reportedly authorising 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’s 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 AFP the victims were all Hamas fighters. 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. 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, the cabinet authorised the callup of 40,000 reservists, unconfirmed press reports said. Officials refused to comment. Around Gaza, dozens of tanks and soldiers could be seen massing along the border, AFP correspondents reported. Defence 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 defence system. So far no Israelis have been killed. Since midnight, Hamas has 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 cancelled within a 40 kilometre (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,” US 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.“Indescriminate 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.