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Mahmoud Abdelbari huddled inside a grimy concrete border passage Monday, caught in a no man’s land between dangerous Gaza and a shuttered exit to Israel.

He was among 300 Gaza residents, mainly with ties to the vanquished Fatah Party, who have spent days here trying to leave for the West Bank. But that requires passing through Israel, and the crossing here has been closed since Hamas took sole control of Gaza and its 1.5 million residents after bloody street fighting last week.

Those in this enclosure, trapped between armed Hamas fighters and Israeli border guards, were low on food and water and high on anxiety. For days an air of desperation has filled the trash-strewn passage, where the Gazans have slept on scraps of wood and made frantic telephone calls seeking help from Palestinian officials to intervene with Israel.

Most worried they might be caught in crossfire between Palestinian fighters on one side of the border and Israeli troops on the other. On Monday evening, they indeed proved to be sitting ducks.

An unidentified Palestinian gunman lobbed a grenade and sprayed gunfire inside the passage, commonly referred to as a tunnel, toward Israeli troops, an Israeli military spokeswoman said. The troops returned fire and at least one of the waiting Palestinians was killed and 17 others injured in the exchange. There were conflicting reports about whether the victims were hit by Israeli or Palestinian weapons.

Umm Mohammed, 36, said she has waited three days with her four children and husband, a former member of the Fatah-led security forces, but that Palestinian officials have done nothing to help.

“We are here all night and day and there is shooting around us. We have no food,” she said.

Israeli human-rights organizations have called on Israel to reopen the borders with Gaza, including Erez and the crucial cargo portal at Karni, to prevent a humanitarian crisis.

The crossing at Karni has been closed since June 11, shutting the supply of a wide range of goods from Israel, including food, and preventing farmers in Gaza from exporting produce.

On Monday, though, an Israeli fuel company resumed sales of gasoline to Gaza a day after announcing it was halting shipments. The company, Dor Alon, did not explain why it reversed course.