Amr Moussa, the Arab League chief, has warned of a humanitarian crisis in Gaza and said Israeli actions could hamper ongoing peace talks.
He urged the international quartet - made up of the United Nations, European Union, Russia and the United States - to put pressure on Israel.
"The quartet must immediately move to stop the series of aggressions and to allow humanitarian aid to enter Gaza in order to end the humanitarian crisis ... and to avoid the collapse of current Palestinian-Israeli talks," Moussa said.
Hosni Mubarak, the Egyptian president, phoned Ehud Olmert, the Israeli prime minister, to stress "the need to stop the Israeli aggression against the Palestinian people" and to warn "of the deteriorating humanitarian situation resulting from the blockade imposed on the [Gaza] Strip by Israel."
The Islamist Hamas movement, which has controlled Gaza since violently seizing power last June, said the Israeli measures amounted to a "slow death" for the territory and called for international intervention.
Mahmoud Abbas, the Palestinian president, also "called on the Israeli government to lift its blockade of Gaza immediately and allow the entry of fuel to facilitate the lives of the innocent and enable the proper functioning of hospitals which are facing a crisis that is putting lives at risk".
Iran renewed its call for foreign ministers of Islamic states on Monday to hold an emergency meeting on the crisis in the Gaza Strip.
Mohammad Ali Hosseini, Iran's foreign ministry spokesman, said: "Iran is ready to host the extraordinary foreign ministers' meeting of the Organization of the Islamic Conference and it is ready to participate anywhere that it is held.
"Iran will participate at the highest level. But it is important to hold the meeting as soon as possible," he said.
Manouchehr Mottaki, the Iranian foreign minister, wrote to Ekmeleddin Ihsanogulu, the OIC secretary general, on Sunday to ask for the ministers' meeting.
But so far the 57-nation OIC has limited its response to a condemnation of Israeli attacks on Gaza and a call for the UN Security Council to intervene to end the punishing Israeli blockade of the territory, now in its fourth day.
Minutes after the power plant shutdown, Gaza residents started a candlelight march. Live Associated Press TV pictures showed dots of light moving slowly up a darkened main street.
Massive rallies were also staged on Monday in Rafah, southern Gaza Strip, Amman, the Jordanian capital, and the Palestinian Shatila refugee camp in Lebanon.
Thousands of university students also protested in Algiers, Algeria's capital, denouncing the blockade imposed on Gaza Strip.
The protesters have also held banners condemning Israel's aggression and holding the international community responsible for the current situation in Gaza.
The Hamas-linked Popular Resistance Committees threatened to break the Israeli blockade by crashing through the border with Egypt "by force."