Israel has closed its crossings into the Gaza Strip, a day after it allowed trucks carrying aid into the besieged coastal territory.
An Israeli defence ministry spokesman said that rocket fire from Gaza towards Israel had prompted the decision to reseal the crossings on Tuesday.
Humanitarian aid groups have warned that the Gaza Strip is dangerously short of essential supplies, despite the delivery of aid on Monday.
Navi Pillay, the UN High Commissioner for Human Rights (UNHCR), urged Israel to allow the flow of aid including food, medicines and fuel to resume, and to restore electricity and water services in Gaza.
Pillay said in a statement: "1.5 million Palestinian men, women and children have been forcibly deprived of their most basic human rights for months."