The war draws together Iran-backed Shia and Sunni militants in what appears to be closer cooperation between groups that differ in ideology but are united by opposition to Israel and the U.S.

The images by Planet Labs PBC show smoke rising over an Abu Dhabi National Oil Co. fuel depot in the Mussafah neighborhood of Abu Dhabi on Monday.

While Abu Dhabi police did not immediately offer any suspects, Yemen's Houthi rebels claimed responsibility for an attack targeting the United Arab Emirates.

The war between the Houthi rebels and the Saudi military has created what the U.N. calls the world's worst humanitarian crisis.

The designation has broad implications — not just for the Iran-backed group, which controls Yemen's capital, but also for international organizations trying to help residents badly in need of aid.