Updated

The U.N. humanitarian chief warns that unless the Saudi-led military coalition lifts its blockade on Yemen the war-torn nation will face "the largest famine the world has seen for many decades with millions of victims."

Mark Lowcock told reporters after briefing the Security Council on Wednesday that there must be an immediate resumption of regular air flights to the cities of Aden and Sanaa by the United Nations and its partner organizations and immediate access to all ports for food, fuel and medicine.

The coalition tightened its blockade in Yemen this week after a ballistic missile fired by Houthi rebels was intercepted near the Saudi capital. The U.N. says aid agencies were given no prior notice of the Saudi decision to shut down all land, air and seaports in Yemen.