A UN agency said Thursday that rebuilding war-wracked Gaza will cost an estimated $30 billion to $40 billion and require an effort on a scale unseen since World War II.

Axar.az reports citing foreign media.

"The United Nations Development Programme's initial estimates for the reconstruction of... the Gaza Strip surpass $30 billion and could reach up to $40 billion," said UN assistant secretary-general Abdallah al-Dardari.

"The scale of the destruction is huge and unprecedented... This is a mission that the global community has not dealt with since World War II," Dardari told a press conference in the Jordanian capital Amman.

He added that if Gaza's reconstruction were to be carried out through the normal process, "it could take decades, and the Palestinian people do not have the luxury of waiting for decades".

"It is therefore important that we act quickly to re-house people in decent housing and restore their lives to normal -- economically, socially, in terms of health and education".

"This is our top priority, and it must be achieved within the first three years following the cessation of hostilities."

He estimated the total rubble from bombardment and explosions at 37 million tonnes.

"We are talking about a colossal figure, and this figure is increasing every day," he said. "The latest data indicates that it is already approaching 40 million tonnes."

The UN official also said "72 percent of all residential buildings have been completely or partially destroyed".