UN agencies called on Israel on Tuesday to allow construction materials into the Hamas-run Gaza Strip so that schools damaged in this year's war can be rebuilt in time for the new academic year.

"We call on the government of Israel to urgently facilitate entry of construction materials and supplies for schools in the coming weeks, and to ensure that students, teachers and trainers can freely exit and enter Gaza to continue learning," they said in a statement.

During the 22-day war that Israel launched on December 27, 280 schools were damaged, including 18 that were completely destroyed.

"Today, one month before the start of the new school year, more than six months after the ceasefires, none of these schools have been properly rebuilt or rehabilitated due to lack of construction materials," the agencies said.

Israel and Egypt have kept Gaza sealed to all but essential humanitarian supplies since the Islamist Hamas movement seized power in the coastal territory in June 2007.

"The blockade has caused untold suffering to children in Gaza, who face another academic year in terrible conditions," said Philippe Lazzarini, the acting UN humanitarian coordinator in the Palestinian territories.

The new school year begins on August 23 in Gaza. More than half of Gaza's 1.5 million population is under 18 years of age.

The Gaza war in December-January killed more than 1,400 Palestinians and 13 Israelis, and left swathes of the aid-dependent territory in ruins.

Among the Palestinians killed, 926 were civilians, 313 of them children, according to Palestinian figures.