Israeli Prime Minister Benjamin Netanyahu on Tuesday announced the launch of a “major operation” in Gaza City, as the Israeli army confirmed it had begun a ground assault aimed at taking control of the city.

The military issued urgent warnings to residents of Gaza City and northern parts of the enclave, calling on them to move south “as quickly as possible” to avoid imminent attacks.

Two Israeli officials told CNN that the ground incursion into Gaza City was already underway and would begin “gradually” in its initial phase.

Residents reported to AFP heavy Israeli bombardments on Gaza City early Tuesday, with widespread destruction and casualties in several neighborhoods.

The offensive marks a significant escalation in Israel’s military campaign against Hamas, which has controlled Gaza since 2007.