Israel's Energy Minister Eli Cohen said on Sunday he had given instructions to stop supplying electricity to Gaza, a week after Israel blocked all aid into the war-ravaged Palestinian territory.
The move has echoes of the earliest days of the war when Israel announced a "siege" that included an electricity cutoff to Gaza.
"I have just signed the order to stop supplying electricity immediately to the Gaza Strip," Cohen said in a video statement, adding: "We will use all the tools at our disposal to bring back the hostages and ensure that Hamas is no longer in Gaza the day after" the war.
The only power line between Israel and Gaza supplies the territory's main water desalination plant, which serves more than 600,000 people.
Gazans depend mainly on solar panels and fuel generators for their electricity.
The connection to the desalination plant was cut off after the October 7, 2023, Hamas attack before being reconnected in July 2024.
But the plant was unable to resume operations until December that year, as the power lines had been too badly damaged by the war.
Last weekend, Israel announced it was blocking aid deliveries to Gaza until Palestinian militants accepted its terms for an extension of the ceasefire which had largely halted more than 15 months of fighting.
The first phase of the truce, which ended on March 1, had enabled the entry of vital food, shelter and medical assistance.
While Israel has said it wants to extend the first phase until mid-April, Hamas has insisted on a transition to the second phase intended to lead to a permanent end to the war.
Hamas on Saturday accused Israel of "committing the war crime of collective punishment" by halting aid and said the move also impacted Israeli hostages still held there.
Of the 251 captives taken during Hamas's October 7, 2023 attack on Israel, 58 remain in the Palestinian territory, including 34 the Israeli military has confirmed are dead.
On Monday, Israeli Prime Minister Benjamin Netanyahu warned Hamas of consequences it "cannot imagine" if it did not release the hostages.
Israeli media reported on Monday that Netanyahu planned to exert "maximum pressure" on Hamas in the coming week to accept an extension of the first phase under Israel's terms.
Public Broadcaster Kan said Israel has drafted plans to ramp up pressure under a scheme dubbed the "Hell Plan".
This included following up the aid block with "displacing residents from the northern Gaza Strip to the south, halting the supply of electricity and a resumption of full-scale fighting."
Israel imposed a "complete siege" on Gaza after October 9, 2023, cutting off water, electricity and food supplies, sometimes loosening and sometimes tightening aid entry until the ceasefire created increased access for humanitarian aid trucks.