Israel is prepared to "significantly widen" its ground offensive against militants in the Gaza Strip, said its Prime Minister Benjamin Netanyahu.
He said the military was targeting the Hamas tunnel network, which it could not do "only from the air".
Operation Protective Edge will continue until it reaches its goal – restoring quiet to Israel's citizens for a prolonged period,»— Benjamin Netanyahu (@netanyahu) July 17, 2014
Thousands of troops moved into parts of Gaza on Thursday night, backed by tanks and artillery fire.
Hamas, the Palestinian group that controls Gaza, has said Israel will "pay a high price" for the invasion.
Gaza update: Netanyahu ordered military to prepare for possibility of "widening, significantly" ground op. http://t.co/b5lVeaVEDe— New York Times World (@nytimesworld) July 18, 2014
"My instructions... are to prepare for the possibility of significantly widening the ground operation, and the military is preparing accordingly," he told reporters before a cabinet meeting on Friday.
At least 24 Palestinians and one Israeli soldier have been killed since the ground offensive began on Thursday.