U.N. spokesman Richard Miron said the explosives were being stored in Gaza until a U.N. team of disposal experts could disarm them, but they disappeared.
The bombs were dropped on Gaza during Israel's offensive there last month, according to another U.N. official. The official, speaking on condition of anonymity because of the sensitivity of the matter, said three one-ton bombs and eight quarter-ton bombs were taken from the warehouse in northern Gaza.
"It's clearly extremely dangerous and needs to be disposed of in a safe manner," Miron said. The material was under guard by Hamas police between Feb. 4 and 14 when it was stolen, he said.
Israeli military spokesman Peter Lerner told The Associated Press that the explosives were probably taken by Hamas. He said Israel had been informed by the U.N. about the missing ordnance.
Hamas officials in Gaza contacted by the AP said they had no knowledge of the matter.
The Israeli Haaretz daily reported that a U.N. bomb disposal team has been working in Gaza for the past three weeks, but it has been hindered by Israeli refusal to allow some of its equipment into Gaza or approve an area for neutralizing the explosives.
The paper said several other warehouses hold unexploded ordnance in Gaza, some close to residential areas. There have been no reports of thefts from other locations.
During the 23-day offensive, Israeli aircraft dropped hundreds of tons of bombs on Gaza and fired artillery and tank shells, aiming at Hamas strongholds but also leveling apartment buildings in areas said to be under Hamas control. About 1,300 Palestinians were killed, about half of them civilians, according to Palestinian figures.
Copyright Associated Press