The ability to bring essential commodities into Gaza was further cut in January by more crossing closures by Israel, the latest United Nations report said on Wednesday, noting that Gaza has been already under the Israeli blockade which is undermining health care, the economy and rehabilitation after last year's devastating Israeli offensive.

The UN and other humanitarian organizations have repeatedly called on Israel to immediately open all border crossings not only for basic necessities, which it allows in limited amounts, but for the reconstruction material needed to rebuild the scores of buildings destroyed by the offensive, which Israel says it launched to halt rocket attacks by Palestinian militants in Gaza.

But in January the situation further deteriorated due the total closure of the fuel crossing at Nahal Oz, which turned Kerem Shalom into the single functional crossing for goods, except for a conveyor belt at Karni Crossing, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said in its monthly report.

"The gradual channeling of all humanitarian shipments to Kerem Shalom since the imposition of the blockade has significantly increased the cost of humanitarian deliveries due to its location, lack of storage capacity, and requirement of the Israeli authorities to repackage containers within pallets," it added.

A month ago, the UN Humanitarian Coordinator for the occupied Palestinian territory, Max Gaylard, warned in a joint statement with the Association of International Development Agencies that the continuing closure was "undermining the functioning of the health-care system.. and causing on-going deterioration in the social, economic and environmental determinants of health."

The blockade was imposed almost three years ago when Hamas, which calls for Israel's destruction, ousted Palestinian President Mahmoud Abbas' Fatah movement from Gaza. Israel allows in a limited amount of food and medicines and other basic necessities but has banned the entry of construction materials which it says could be used for aggressive purposes.

Last year's Israeli offensive destroyed or damaged 15 of Gaza's 27 hospitals, and 43 of its 110 primary health-care facilities.

UN Secretary-General Ban Ki-moon, in a report issued last November, stressed that the blockade of vital supplies has devastated Gaza's economy and "has also severely impaired the realization of a wide range of economic, social and cultural rights, as well as civil and political rights."