The United Nations on Wednesday demanded media access to report on the “man-made catastrophe” in Yemen after a Saudi Arabia-led coalition blocked three foreign journalists from traveling on a U.N. aid flight to the Houthi rebel-controlled capital Sanaa.

“Steps like this do not help,” U.N. spokesman Farhan Haq told reporters in New York. “This has been a large man-made humanitarian problem, the world needs to know and journalists need to have access.”

The coalition, which intervened in the Yemen conflict in 2015 in support of the internationally recognized government of President Abd-Rabbu Mansour Hadi, controls the airspace over Yemen and can prevent any flights made without prior permission.

The Saudi-led coalition, which is backing Yemen government forces fighting the Iran-allied Houthi rebels, prevented the U.N. flight from departing Djibouti on Tuesday because the journalists were due to travel.