Israel announced a major expansion of military operations in Gaza on Wednesday, saying large areas of the enclave would be seized and added to its security zones, accompanied by large-scale evacuations of the population.

Israel said it sent ground troops back into the center and south of the Gaza Strip, expanding a military operation that began with airstrikes a day earlier that Palestinian authorities said killed hundreds of people.

Israeli Prime Minister Benjamin Netanyahu said Israel’s military is “switching gears” in Gaza, dividing and seizing more parts of the strip, a move experts say could mean Israel establishing deeper, more long-term control over the territory.