The Israeli military has launched what could be a long-term offensive against the Hamas-ruled Gaza Strip, striking at least 50 sites in Gaza and mobilising troops for a possible ground invasion aimed at stopping a barrage of rocket attacks against Israel.

Smoke rises following what witnesses said was an Israeli air strike in Gaza City
Smoke rises following what witnesses said was an Israeli air strike in Gaza CityReuters
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An Israeli soldier performs a morning prayer in a deployment area near Israel's border with the Gaza StripAFP
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An Israeli police explosives expert holds the remains of a rocket fired from Gaza after it landed in Kibbutz NirimReuters
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An Israeli military Apache helicopter fires a missile over the Gaza StripAFP

 The military said "Operation Protective Edge" aims to strike the Islamic Hamas group and end the rocket fire that has penetrated deeper into Israel and intensified in recent weeks amid tensions over the killing of three Israeli teenagers and the apparent revenge killing of a Palestinian teenager.

Nearly 300 rockets and mortars have been fired at Israel in recent weeks, including a barrage of close to 100 projectiles on Monday alone, Israel said. This represents a huge surge after years of relative quiet that followed a previous campaign to root out Gaza rocket launchers.

Israel has responded with dozens of airstrikes. The government in Jerusalem has previously signalled that it will not launch a larger offensive if the militant group Hamas ceased the rocket fire.

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Smoke rises after an Israeli air strike in the northern Gaza Strip, as seen from the Israeli side of the borderReuters
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A ball of fire is seen following an Israel airstrike on Gaza International Airport in RafahAFP
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Palestinians carry their belongings from a house in Khan Younis in the southern Gaza Strip, which witnesses said was destroyed in an Israeli air strikeReuters
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A Palestinian boy inspects a house which was destroyed in a reported Israeli air strike in Khan Younis in the southern Gaza StripReuters

After a brief early morning lull, the rocket fire from Gaza has resumed, with more than 15 rockets fired toward southern Israel, including the cities of Ashdod and Ashkelon. The Israeli military said five were intercepted by the country's sophisticated Iron Dome missile defence system.

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Israel's anti-missile Iron Dome air-defence system fires to intercept a rocket over the city of AshdodGetty
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An Israeli police explosives expert holds the remains of a rocket fired from Gaza after it landed in Kibbutz Nirim. The Israeli military has hit at least 50 sites in Gaza by air and sea and is mobilising troops for a possible ground invasion aimed at stopping a recent barrage of rocket attacks against IsraelReuters

The Israeli military said the 50 sites it has targeted in Gaza include four houses belonging to Hamas militants involved in launching rockets at Israel or other militant activity. In addition, the military said it struck three militant compounds, 18 concealed rocket launchers, and other militant infrastructure sites.

Gaza health official Ashraf Al-Kedra said at least nine Palestinian civilians were brought to a Gaza hospital with light to moderate injuries from the airstrikes.

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A destroyed building is seen following an Israeli military strike in Gaza CityAFP
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Israeli flares illuminate the Palestinian coastal enclaveAFP
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A Palestinian man who, medics said, was wounded in an Israeli air strike, is treated at a hospital in Khan Younis in the southern Gaza StripReuters

 An Israeli military spokesman said the army will gradually increase its attacks on Hamas in Gaza, and is recruiting additional reservists for a potential ground invasion.

Israeli tanks and buses have gathered near the border with the Gaza Strip in preparation for a possible land offensive.

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Israeli soldiers stand next to tanks positioned on the Israeli side of the border with the Gaza StripAFP
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An Israeli soldier sleeps with a mosquito net on his face in a deployment area near Israel's border with the Gaza StripAFP

 The increased rocket fire followed the killing of Mohammed Abu Khudeir, a 16-year-old Palestinian boy who was abducted and burned to death last week.

Israeli officials have announced the arrests of six Jewish youths in the killings, saying the suspects included two brothers and the son of a rabbi.

Tensions have been high since three kidnapped Israeli teenagers were found dead, which prompted the killing of Khudeir in a possible revenge attack.

About 50 people were arrested in several days of demonstrations following Khudeir's death, and the victim's 15-year-old Palestinian-American cousin was injured in clashes with Israeli security forces in east Jerusalem.

Naftali Frenkel, Gilad Schaer and Eyal Yifrah
The three kidnapped Israeli teenagers: Naftali Frenkel, Gilad Schaer and Eyal YifrahReuters
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Mohammed Abu Khdueir, a 16-year-old Palestinian from east Jerusalem, who was abducted near his home. His charred remains were found shortly afterward in a Jerusalem forest. Israel has arrested suspects in the death of the Palestinian teenagerReuters
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Tariq Khadair is greeted by his mother after being released from jail in Jerusalem. Tariq Khadair from Tampa, Florida, is a cousin ofMohammed Abu Khudeir.Reuters