"Since early Friday evening, combined combat forces of armour, combat engineers and infantry have been operating on the ground in the northern Gaza Strip," an army statement said.

Israeli forces have made several smaller-scale ground incursions inside Gaza, but the current one has been their longest presence in the territory since violence erupted with a deadly Hamas assault on October 7.

Earlier on Saturday, Israeli Defence Minister Yoav Gallant said the war had "entered a new phase" with the intense overnight bombing campaign.

"Last night the ground in Gaza shook. We attacked above ground and below ground," Gallant said in a video statement, alluding to the network of military tunnels Hamas has built under Gaza.

"The instructions to the forces are clear: the action will continue until further notice."