Pictures of the late Yasser Arafat, left, and Palestinian President Mahmoud Abbas have been ripped off the walls of Abbas' personal office in Gaza City after it was taken over by Hamas militants. Fatah forces collapsed under the onslaught by Hamas, which showed superior organization and motivation.

Jerusalem ? The urban warfare that convulsed the Gaza Strip this week was bad enough, diminishing already scarce food, fuel and medicine in the impoverished Palestinian territory.

But the battle’s decisive outcome seemed only to make things worse: Relief from what international aid workers call a humanitarian crisis now depends on cooperation between Israel, which controls most of the fenced-in territory’s border crossings, and the victorious Hamas gunmen on the other side.

So far the two sworn enemies aren’t speaking to each other. As a result, Gaza remained sealed off to the world Friday, even as aid workers warned of looming shortages of basic necessities.

“I am watching what is happening and worrying that Israel and other countries will turn Gaza into a prison,” Ahmad Abdel Rouf, a father of 12, said as he scrounged shops for food and loaded up his donkey cart in Khan Yunis, a city in southern Gaza.

The 55-year-old, who said he supports Hamas, echoed a fear of many other Palestinians that the militant Islamic movement’s rout of its secular Fatah rival may leave the victors incapable of providing for Gaza’s 1.4 million people.

Until this week, Hamas and Fatah shared power in the Palestinian Authority government that runs Gaza and the West Bank. Because Hamas refuses to recognize Israel and advocates its destruction, Israel and Western countries imposed a financial blockade on the two territories last year while permitting restricted passage of commercial cargo and humanitarian relief supplies.

Those goods, including United Nations-administered food aid to two-thirds of Gaza’s population, passed into Gaza through border crossings under U.S.-supervised agreements between Israeli and Fatah officials who coordinated with each other over walkie-talkies.

But this week’s fighting forced the border crossings to close, and when it ended Thursday night Israel’s vanquished Fatah counterparts were nowhere to be found.

Israeli officials said the sudden turn of events put them in a quandary: How to let in relief supplies and avoid an explosive social crisis in Gaza without abandoning its policy of refusing to cooperate with Hamas.

“We are aware that the humanitarian conditions in Gaza are not good, and no one in Israel wants to see them get worse,” said Mark Regev, spokesman for Israel’s foreign ministry. “But obviously the new situation has to be digested and we have to find ways to make things work.” Hamas appeared in no bigger rush to reopen Gaza’s border terminals.

Ismail Haniyeh, the Hamas prime minister, did not mention a need for open borders or international relief in a lengthy address Friday outlining his policy priorities and justifying his refusal to leave office. His Cabinet had been formally dissolved late Thursday by Palestinian Authority President Mahmoud Abbas, the Fatah leader based in the West Bank.

Hamas gunmen with laptop computers took up positions Friday at the Erez, Karni and Rafah border crossing posts, witnesses said. But the gunmen’s sole apparent mission was to keep the border closed and prevent wanted Fatah rivals, whose names were stored on their hard drives, from fleeing the Gaza Strip.