A senior United Nations official says many families in Gaza are facing a life-or-death situation as Israel continues its military offensive against Hamas.

U.N. humanitarian coordinator Maxwell Gaylord released a statement Wednesday calling on Israel to allow more humanitarian aid to flow into Gaza, which has been under a blockade.

Israel has said it will allow 2,000 tons more of food and medical supplies into Gaza, and will allow some wounded Gazans to seek medical treatment in Israel.

But Gaylord says it is crucial for the Karni border crossing to be opened to allow in wheat grain for the 750,000 people who rely upon U.N. relief. He also says electricity needs to be fully restored to Gaza's hospitals, which are overwhelmed with patients.

Many other world powers and human rights groups have expressed concern about the humanitarian situation in Gaza.