REPUBLIKA.CO.ID, GAZA/JERUSALEM - Israel launched a Gaza ground campaign after 10 days of bombardments from the air and sea failed to stop militants' rocket attacks, stepping up an offensive that already has taken a heavy toll in civilian lives.

A witness in northern Gaza said that several tanks had rolled through Israel's Erez border crossing to the Palestinian side but had stopped short of residential areas, and that no clashes had ensued.

Israel signalled the invasion would be limited in scope - targeting tunnels dug by gunmen - and said it was not intended to topple Hamas, the Gaza Strip's dominant Islamist group. Explosions lit up the sky in the early hours of Friday and residents in several areas of the densely populated strip of 1.8 million Palestinians said they saw small numbers of Israeli tanks that had crossed the border from Israel.

A statement from Prime Minister Benjamin Netanyahu's office late on Thursday said he had given orders to destroy tunnels that militants use to infiltrate Israel and carry out attacks. An Israeli military spokesman said Israel was not out to try to topple Hamas.

Hamas spokesman Sami Abu Zuhri responded with defiance to Israel's invasion announcement, telling Reuters: "We warn Netanyahu of the dreadful consequences of such a foolish act."

Gaza residents and medical officials reported heavy shelling along the eastern border from the southern town of Rafah to the north of the strip. Residents said heavy clashes took place along the border, including in the northern towns of Beit Hanoun and Beit Lahiya.

Orange flashes illuminated the eastern Gaza Strip as Israeli gunboats off the Mediterranean coast fired shells and tracer bullets. Israeli artillery pounded the area and helicopters fired across the border, Reuters witnesses said. Rockets streaked from Gaza toward the southern Israeli towns of Ashdod and Ashkelon. Live television showed interceptions by the Iron Dome anti-missile system, and no casualties were reported.

Israel last mounted a large-scale invasion of the Gaza Strip during a three-week war in late 2008 and early 2009 that claimed 1,400 Palestinian and 13 Israeli lives. No time frame was announced for the new operation, and the length and intensity of Israel's assaults could depend on the scale of civilian deaths - casualties likely to boost international pressure for a ceasefire.

At least 240 Palestinians had been killed in Israeli air strikes since July 8, many of them children, medics in Gaza said quoted by Daily News. An NGO based in the coastal enclave saying 80 percent of the deaths are civilians.

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