The number of Gazans living in "abject" poverty has tripled this year to 300,000, or one in five residents, the Gaza head of the U.N. agency helping Palestinian refugees said Thursday.

Gaza's economy has foundered under an Israeli-Egyptian border blockade imposed after the Islamic militant group Hamas seized control of the territory in 2007 from forces loyal to Palestinian President Mahmoud Abbas.

John Ging, the U.N. Relief and Works Agency's top official in Gaza, called the rise in poverty a "predictable consequence" of the border blockade.

"The suffering, the impoverishment, the misery of the people here in Gaza continues to rise because of a man-made crisis, a political failure," Ging told reporters.

The blockade's toll on Gaza residents was compounded by Israel's winter offensive in the strip that aimed to stop Palestinian rocket fire at southern Israel. Thousands of homes, government buildings and businesses were destroyed during the Israeli campaign.

U.N. staff said the rise also reflects improved monitoring of refugees' economic conditions.

The U.N. agency provides services, including emergency food rations, to 750,000 of Gaza's 1.4 million residents. Those who are unable to feed their families are considered "abject poor" and receive extra aid, the agency said.

Ging said lifting the blockade is the only way to stop Gaza's rising poverty, and appealed for more funding to help his agency meet the growing need.

Israeli officials have said they fear that easing the blockade will benefit Hamas, and say they won't reopen the border crossings until the militant group releases an Israeli soldier captured more than three years ago.

A first sign of progress toward a prisoner exchange emerged Wednesday when Israel agreed to release 20 Palestinian women from its prisons in exchange for a recent video of the soldier.