JERUSALEM — Israeli troops and tanks invaded the Hamas-ruled Gaza Strip late Saturday after eight days of punishing airstrikes failed to halt the militant Palestinian group's rocket fire into Israel.
Gun battles and explosions could be heard from Gaza City as high-rise buildings shook and artillery rounds lighted the night sky. Columns of tanks and infantry, backed by helicopter gunships, pushed nearly half a mile into the territory from three directions.
Medical authorities in Gaza reported today that five militants and three civilians were killed in the early hours of ground fighting. Israel said 30 of its soldiers and "dozens" of militants were wounded.
Israeli officials said they expected a lengthy battle but did not intend to remain in Gaza.
"This will not be easy and it will not be short," Israeli Defense Minister Ehud Barak said.
Hamas issued a defiant statement saying Gaza would "become a graveyard" for Israeli soldiers. Later, its radio and TV stations went off the air, apparently disrupted by the Israelis.
The ground offensive, involving thousands of soldiers, was aimed primarily at Hamas' rocket-launching facilities, Israeli officials said. Some of those sites are in open fields, but many are hidden across Gaza in densely populated areas and are difficult to pinpoint from the air.
In choosing to strike from the ground as well as the air, Israel undertook two risks: Its army could get bogged down in a messy fight with a determined paramilitary foe. And Palestinian civilian casualties could rise sharply, increasing international pressure on Israel to halt the operation.
Israel's airstrikes have already taken a heavy civilian toll. A missile demolished part of a mosque Saturday in the northern town of Beit Lahiya during late afternoon prayers, killing 13 people and wounding 33 inside, a Palestinian medical official reported. Two of the dead were children, he said.
The strikes began Dec. 27, a week after Hamas let an Egypt-brokered truce lapse. The six-month cease-fire had begun to break down in November.
More than 460 Palestinians have been killed in the operation, Palestinian officials say. About one-fourth of them were civilians, according to the United Nations' tallies.
Yet the rocket fire by Gaza militants has continued. Three Israeli civilians and one soldier have been killed in the last week, as Hamas deployed more advanced, longer-range projectiles capable of hitting Israeli cities more than 20 miles away.
