( dpa ) - The de facto Hamas administration in the Gaza Strip warned of a "catastrophe" if Israel did not end its total lock-down of the coastal salient, which entered its fourth day Monday.
"The situation is disastrous," Ismail Radwan, a spokesman for the radical Islamic ruling the Strip, told reporters in Gaza City.
Warning of a "big explosion" that would have "consequences on the entire region," he urged Egypt to open its border with the Gaza Strip to medical supplies, food and fuel.
Responding to a barrage in rocket and mortar attacks, Israel completely shut down its border crossings with the Gaza Strip, including its Nahal Oz crossing with the south of the salient, which had thus far remained open to shipments of basic necessities, including key food products, drugs and fuel.
Gaza's only powerplant, which operates on industrial diesel, shut down Sunday evening, leaving large parts of the Strip in darkness and without power.
The shutdown affects mainly Gaza City and its surrounding suburbs, which are supplied by the powerplant.
Rafik Maliha, the head of the plant, said this meant some 800,000 Gazans were without electricity since Sunday evening.
According to the Palestinian Centre for Human Rights (PCHR), the Gaza Strip needs some 230 megawatts of electricity a day. Its only local powerplant supplies some 30 per cent of that, or 65 megawatts.
Israel however has accused Hamas of exaggerating the humanitarian situation in Gaza for "propaganda" purposes.
It pointed out that while its crossings with the Strip are closed, its own powerplants continue to supply 124 megawatts of electricity to the Strip, in addition to another 17 megawatts provided by Egypt. A government statement said that makes up three-quarters of Gaza's daily needs.
Israeli defence officials said Monday that total closure of Gaza would continue for the time being.
But responding to widespread warnings, Israeli Prime Minister Ehud Olmert said Monday Israel would avoid a humanitarian disaster in the Strip.
"We will continue to transfer food, medicine and additional basic goods to Gaza," Israeli media quoted him as telling visiting Dutch Foreign Minister Maxime Verhagen.
"We are refraining from creating a humanitarian crisis in the Strip," he said, but stressed Israel would continue to block the entry of non-basic goods. " Israel won't play in the hands of Hamas."
The European Union earlier warned that Israel's decision to tighten its closure on Gaza "will exacerbate an already dire humanitarian situation in the Gaza Strip."
European Union's Commissioner for External Benita Ferrero-Waldner in a statement also condemned the move as "collective punishment."
Egyptian President Hosny Mubarak also made separate telephone calls to Olmert and Israeli Defence Minister Ehud Barak, urging them to end the total blockade, Egypt's state news agency MENA reported.
Israeli soldiers meanwhile shot dead an Islamic Jihad militant in an exchange of fire in the West Bank city of Tulkarm, which also lightly injured an Israeli officer.