GAZA CITY (CNN) -- Israel agreed Monday to relax a blockade of Gaza after fuel shortages left residents struggling with severe power cuts amid concerns from aid agencies of a humanitarian crisis.
A Palestinian man uses a lantern at his shop after the power was cut in Gaza City on Sunday.
According to a spokesman from the defense ministry, Israel will allow one shipment of diesel fuel and medications into Gaza on Tuesday. The ministry will then consider if further shipments will be allowed, he said.
It closed all border crossings between Israel and the Palestinian territory on Friday after days of rocket attacks on southern Israel.
The block on the entrance of fuel, food, and medicine has led to long lines at bakeries, left hospitals without heat and gas stations closed. The Israeli government said any Palestinians who need medical treatment would be allowed to cross.
Much of Gaza was in the dark Sunday night and Monday. Long lines stretched around bakeries, some of which had to shut because their power supply was cut; use of generators was limited for fear the fuel used to operate them would run out.
At Shiffa Hospital in Gaza City, patients lay next to blank monitors and other equipment that was turned off. Watch people gathering with candles in the streets of Gaza »
CNN's Ben Wedeman said from Gaza one hospital had lights only in the intensive care unit, and that doctors on the wards were using candles and flashlights.
John Ging, head of the United Nations' Relief and Work Agency in Gaza, told CNN by phone from Gaza that hospitals had switched off their heating systems to preserve power. Ging said residents were "living day to day."
He estimated that the United Nations had reserves of food to last two more months, and that nylon bags for distributing aid would run out in a week after a delivery was stopped last week at the border.
"We need fuel in Gaza. There is no other way to avoid a disaster," Ging told CNN.
He criticized the blockade, accusing the Israeli government of carrying out "collective punishment" of a civilian population, which he said is outlawed under international law.
He said the rocket attacks from Gaza were deplorable but the Israeli reaction should be "proportional and appropriate." He added that Gazan civilians are just as much victims of the conflict as the Israelis.
An Israel-based human rights group which advocates easing of movement for Palestinians said the closing of the borders was "paralyzing" vital systems in Gaza like hospitals, water and sewage pumps, and schools.
The group, Gisha, said that without fuel, Gaza's power plant would have to shut down.
Gaza receives about 70 percent of its electricity from Israel, and the bulk of the remaining power comes from a generation plant in Gaza. That plant relies on fuel supplied by an Israeli company.
The Israeli Foreign Ministry said claims by Hamas -- which controls Gaza -- of a humanitarian crisis were "greatly exaggerated."
"While the fuel supply from Israel into Gaza has indeed been reduced, due to the Hamas rocket attacks, the diversion of this fuel from domestic power generators to other uses is wholly a Hamas decision -- apparently taken due to media and propaganda considerations," a Foreign Ministry statement read.
"Noteworthy is the fact that while the Gaza population remains in the dark, the fuel generating power to the Hamas rocket manufacturing industry continues to flow unabated."
The Foreign Ministry said there was no shortage of basic foodstuffs in Gaza.
Gisha said Gaza's residents were already suffering an electricity deficit of 35 percent and that the number would increase to 48 percent if the Gaza power plant were to shut down.
"We condemn the illegal rocket attacks on civilians in southern Israel," Gisha said in a statement. "But punishing Gaza's 1.5 million civilians does not stop the rocket fire; it only creates an impossible 'balance' of human suffering on both sides of the border." E-mail to a friend