'Preparing for next stages of war'

"We are preparing ourselves for the next stages of war... to prepare for multiple operative contingency plans," Israeli army spokesman Richard Hecht said.

He said the possible operation "could be from the air, it could be combined from the sea (and) air".

Israel's assault is targeting senior leaders of Hamas, Lt-Col Hecht said, including the group's chief in Gaza, Yahya Sinwar.

"Right now we are focused on taking out their senior leadership, not only the military leadership (but) also their governmental leadership, all the way up to Sinwar," Lt-Col Hecht said.

"They were directly connected" to the weekend attack, he added.

In a separate briefing to reporters, chief military spokesman Rear Admiral Daniel Hagari reiterated the army's plans against the Islamists.

"We are crushing Hamas' ability to function as sovereign," he said.

"It is already failing to run Gaza in some areas," he continued, adding that they would continue to target the group until it is no longer able to rule "in all of Gaza".