Israel justified the cutoff because of continuous rocket attacks by Gaza militants.
Arye Meckel, spokesman for the Israeli Foreign Ministry, said the Gaza Strip continues to receive 70 percent of its electricity supply directly from Israel, which would not be affected, and another 5 percent from Egypt.
The blackout "is a Hamas ploy to pretend there is some kind of crisis to attract international sympathy," he told the Associated Press.
Late yesterday, the Palestinian president, Mahmoud Abbas, appealed to Israel to lift the blockade, said Abbas spokesman Nabil Abu Rdeneh. Abbas effectively rules only the West Bank after Hamas expelled his forces from Gaza last June.
The exiled leader of Hamas appealed to Abbas and Arab leaders, asking them to forget their differences and help the beleaguered Gazans.
"All Arab leaders, exercise real pressure to stop this Zionist crime . . . take up your role and responsibility," Khaled Mashaal told Al-Jazeera satellite TV in a live interview from Syria, where he lives in exile. "We are not asking you to wage a military war against Israel . . . but just stand with us in pride and honor."
Officials from the ruling Islamic militant group Hamas shut down the plant just before 8 p.m. and Gaza City went dark, Gaza Energy Authority head Kanan Obeid said. TV crews and reporters were invited to witness the shutdown.
Minutes later, residents started a candlelight march as a protest. Live Associated Press TV pictures showed dots of light moving slowly up a darkened main street.
Israel has blockaded Gaza for seven months, since the Islamic militant Hamas overran the territory, allowing up until now only basic food items and humanitarian supplies into Gaza.
That changed Thursday when Defense Minister Ehud Barak ordered all crossings into Gaza closed because of a spike in rocket barrages, cutting off fuel supplies. Several weeks ago, Israel reduced the fuel supply as a pressure tactic.
A defiant Hamas said its attacks on Israel would not cease because of the sanctions.
"We will not raise the white flag, and we will not surrender, " Hamas spokesman Sami Abu Zuhri said yesterday.
The regular fuel shipment from Israel did not arrive yesterday because the fuel terminal was closed, and the power plant has almost no reserves, said Rafik Maliha, director of the power plant.
The UN organization in charge of Palestinian refugees warned the blockade would drastically affect hospitals, sewage treatment, and water facilities.
"The logic of this defies basic humanitarian standards," said Christopher Gunness, spokesman for the UN Relief and Works Agency, or UNRWA.
The British group Oxfam called Israel's cutoff "ineffective as well as unlawful."
