JERUSALEM — Israeli ground forces backed by air and naval power fought their way into urban areas deep inside the Hamas-ruled Gaza Strip on Monday, striking at the Palestinian group's strongholds but also inflicting a heavy toll in civilian lives.
Medical authorities in Gaza said 20 children were killed by airstrikes, naval shelling and artillery fire that Israel said it was aiming at Hamas' 15,000-man paramilitary force. Three Israeli soldiers were killed in a "friendly fire" incident.
Palestinians said Israeli attacks intensified before dawn today, hours after troops had entered densely populated areas just north and east of Gaza City. Witnesses said they took up positions atop several six-story buildings on the outskirts of the city, which has a population of 400,000.
In Washington, U.S. officials outlined elements of a proposed truce that met some of Israel's conditions. But Israeli officials insisted on more time to press the offensive, now in its 11th day, and said it could go on for days if not weeks.
Hamas, too, vowed to keep fighting and fired at least 31 rockets into Israel on Monday, including one that struck an empty kindergarten in the city of Ashdod.
"They want to drag us into urban areas," Defense Minister Ehud Barak told a parliamentary committee Monday. "The main test could still be ahead."
A spokesman for Hamas' military wing, using the nom de guerre Abu Obeida, warned Israel that militants "wait for you in every street and every alleyway."
The Israeli offensive is aimed at stopping rocket fire by Palestinian militants.
Hamas, an Islamic group whose charter calls for Israel's destruction, seized control of Gaza after routing the rival Palestinian faction Fatah in mid-2007, two years after Israel unilaterally withdrew its settlements and military bases.
After eight days of air raids, Israel sent tanks and troops into the 140-square-mile territory Saturday.
As Israeli jets and naval ships bombarded the southern part of the strip, striking tunnels used to bring in weapons from Egypt, tank and infantry units punched into the north. They met limited resistance over the weekend as they moved cautiously through open fields before reaching Hamas' urban strongholds and rocket-launching sites late Monday.
Heavy air and artillery fire erupted after dark near Jabaliya as Israeli forces battled for control of a hill overlooking that city and its sprawling refugee camp.
