Israel has told civilians to flee south ahead of a possible ground invasion in northern Gaza as the conflict moves into its next stage.
Following heavy bombardment on Saturday, the Israeli Defence Forces (IDF) said the country's objectives now require a "ground operation".
Reports had stated that troops had crossed the border overnight into northern Gaza and had remained in the battlefield.
"Our forces are currently operating on the ground in the Gaza Strip," IDF chief of staff Herzi Halevi said.
"In order to expose and destroy the enemy, there is no other way than to enter its territory with force."