A U.N. official said a truck carrying aid was turned around in Gaza this week because it contained scissors included in medical kits for children, calling attention to what aid groups have said is a laborious Israeli inspection process that is slowing down crucial humanitarian assistance.

Philippe Lazzarini, the head of UNRWA, the main U.N. agency providing support for Palestinians in Gaza, said the truckload had been refused because medical scissors had been added to a list of items the Israeli authorities consider to be “dual use,” or having both civilian and military purposes.

COGAT, the Israeli agency overseeing aid deliveries into Gaza, accused Mr. Lazzarini of lying, saying that it was in constant contact with the United Nations and had not been notified of the denial. The agency said 1.5 percent of aid trucks trying to enter the territory had been turned away.

Mr. Lazzarini is the latest official to say that the Israeli military’s inspections are keeping aid from getting to Gaza’s 2.2 million people. Last week, Britain’s foreign minister, David Cameron, said during a parliamentary debate that “too many” goods were being turned away for being dual use, including items that are medically necessary.

A member of the British Parliament said this month that Israel had turned away 1,350 water filters and 2,560 solar lights provided by the British government because they were considered a threat.

Miriam Marmur, director of public advocacy at Gisha, an Israeli nonprofit that works to protect the free movement of Palestinians, said Israel’s list included broad categories that can encompass thousands of items, making it difficult to know what is prohibited. Many items that have been turned away aren’t explicitly listed, she said.