Israeli demolitions of Palestinian homes in the occupied West Bank rose "alarmingly" in the first half of 2011, in some cases threatening entire communities, a United Nations agency said on Tuesday.

The UN Relief and Works Agency, which looks after Palestinian refugees, said 356 structures had been demolished in the first six months of this year, compared with 431 for the whole of 2010.

And the agency said 700 people had been displaced by the demolitions in the first six months of 2011, compared with 594 in the whole of 2010.

"Demolitions by the Israeli authorities in the West Bank have escalated alarmingly," said UNRWA spokesman Chris Gunness.

"Most demolitions have targeted already vulnerable Bedouin and herding communities," he said. "In many cases, demolition orders have been issued to virtually the whole community, leaving these communities facing a real danger of complete destruction."

The demolitions are taking place in Area C, the 60 percent of the West Bank that is designated as under full Israeli control, in which Israel has designated just one percent of land for Palestinian development, UNRWA said.

"This mean that it is virtually impossible for a Palestinian to obtain a permit for construction, while Israeli settlements receive preferential treatment in the allocation of water and land, and approval of development plans," Gunness said.

Israel says its demolitions of homes are based only on whether the structures in question have the appropriate permits.

But the agency said the demolitions seemed to be concentrated in areas "targeted for settlement expansion."

"Most disturbing of all is the clear link we now see between settlement expansion and demolitions and the forced displacements that result," Gunness told AFP.

UNRWA called on the Israeli government to immediately halt demolitions of Palestinian homes "until Palestinians have access to a fair and non-discriminatory zoning and planning regime."