The United Nations demanded Wednesday that Israel implement a five-year-old ruling of its International Court of Justice (ICJ) in The Hague that deemed most of the West Bank separation fence illegal.

The fence severely restricts the movement of tens of thousands of Palestinians, the UN's Office for the Coordination of Humanitarian Affairs (OCHA) told a news conference in Jerusalem, marking the fifth anniversary of the ICJ advisory opinion.

Some 85 per cent of it was built inside the West Bank, and not on the Green Line.

Some 35,000 Palestinians are trapped in the closed area between the fence and the Green Line, some 10,000 of whom need special permanent resident permits to enter the West Bank.

Palestinians wishing to enter the closed area for family, economic, health or educational reasons need visitor permits, which are difficult to obtain from the Israeli government, OCHA said.

"Life of people in the West Bank and in the closed area is reduced to a piece of paper," Michael Baily, of the British NGO Oxfam, told the news conference, referring to the permits.

He urged the international community to pressure Israel toward implementing the ICJ advisory opinion.

Five years after the ruling, Israel is continuing construction of the barrier and has added another 200 kilometers to it, OCHA said. So far, 413 out of a total 709 kilometers of the barrier are ready.

It charged that the route Israel was choosing for the barrier was "not necessary to attain its security measures."

Israel decided to build the barrier at the height of an unprecedented wave of suicide bombings in 2002. It says it is choosing the route to protect as many Israeli citizens as possible, including settlers.