A former Israeli intelligence chief warned on Monday that Hamas's 7 October attacks could result in the destruction of "its capital", appearing to refer to Gaza City.
Amos Yadlin, former head of the Israeli military's intelligence department, told the BBC that an Israeli ground assault would wreak further damage to Gaza, as Israeli tanks appeared to surround the besieged enclave's de facto capital.
Yadlin appeared to hint that Gaza City's destruction would likely send a message to the rest of the Arab world of the price for targeting Israel.
"Everybody in the Middle East will understand that if you will kill Israeli children and women, its capital is going to be destroyed, and the organisation that controls this capital is going to not exist. This is what Israel is planning," he told BBC radio.
Such a tactic of collective punishment could be considered a war crime and open military commanders to prosecution in international courts.
The threat came as Israeli armour appeared to move to the north and south of Gaza City, cutting off the last route out for thousands of civilians trapped there.
The message also appeared to be a warning to Hezbollah and Iran not to get involved in the conflict, following skirmishes on the Lebanon-Israel border.
Israel has bombarded Gaza since 7 October, when Hamas and other fighters broke out of besieged Gaza and killed an estimated 1,400 Israelis.
Since then, more than 8,300 Palestinians in Gaza have been killed – around half of them children, indicating that Israel is already pursuing a campaign of indiscriminate bombing in the enclave.
Israel has also ordered a complete siege on Gaza, cutting off food, water, medicine and fuel and threatening thousands more lives.
Gaza has been under siege for more than 15 years, with waves of Israeli aerial bombing campaigns killing thousands of civilians.