GAZA CITY, Gaza — Palestinian Arabs filled up containers with gasoline and waited in hour-long lines at bakeries as Israel and the Palestinian Authority in the West Bank began tightening the screws on the Hamas-controlled Gaza Strip yesterday.

Gaza’s lone fuel supplier, the Israeli energy company Dor Alon, halted fuel supplies to the territory, which was seized by the Islamist Hamas movement on Thursday after five days of civil war with the rival Fatah movement.

A new Fatah-controlled Palestinian Arab government in Ramallah, meanwhile, made its priorities clear on being sworn in. Its first act was to freeze all accounts connected to ministries in the disbanded unity government with Hamas.

At a gas station in northern Gaza, the owner, Nabil Nasr, said he would be out of fuel by morning. Supplies throughout the coastal strip would dry out by Wednesday, he said.

“My last delivery was three days ago, and usually, I get deliveries every day,” he said.

Gas flows into the Gaza Strip at the Nahal Oz crossing, where Israel tankers pump it across the border into underground tanks on the Palestinian Arab side.

The guards of President Abbas of Fatah had held it until last week, when the elite security service dissolved in the face of the Hamas onslaught.

Israel is unlikely to warm to the idea of Hamas, which is funded by Iran and which last summer tunneled under the Gaza border to kidnap an Israeli soldier, taking hold of the sensitive terminal.

Mr. Nasr worried that the longtime foes would not work together even to secure the most rudimentary daily needs for the Gaza Strip.

“Hamas doesn’t recognize Israel, so how can they recognize Israeli gas,” he said.

Wissam Aziz, 25, filled up 20-liter cans with fuel and topped up his tank as he braced for the looming shortages. His grain supply business would halt if his lorries cannot make deliveries.

“I fear the Israeli boycott,” he said. “We have been living under siege for more than a year, and now it’s going to get worse.”

Prime Minister Olmert of Israel said his government would work with aid organizations to keep food and medicine flowing into Gaza even as small number of Israeli tanks moved into northern Gaza amid looting and chaos at the Erez border crossing.

The inability of Hamas and Israel to co-ordinate Gaza’s daily needs also took a toll on Abu Shaban, 37, and hundreds of other Palestinian Arabs waiting in vain to flee Gaza for the West Bank at the crossing.

Mr. Shaban, an intelligence officer in the ousted Fatah-run security services in Gaza, fears Hamas retribution. He said he has no choice but to leave his wife and four children behind in Gaza as he sought refuge in the Fatah-controlled West Bank.

But with no Palestinian Arab authorities with which to co-ordinate and with swarms of people mobbing the crossing, Israel has slammed the door on all but a few would-be emigrants.

Hamas erected checkpoints about a quarter of a mile away, checking IDs of those trying to flee, seeking out Fatah fighters.

Mr. Shaban carried football kit and convinced the Hamas gunmen that he was on a Gaza team that had a match in Jordan. “I hope I will be able to come back to Gaza some day,” he said.

A fellow intelligence officer, Abu Abdallah, 31, sat next to him.

He held up a picture of his seven-year-old daughter Ghadeer, who he was leaving behind, and buried his face in his hands to hide the tears.