A blast struck a military graduation parade in Yemen's southern town of al-Dhalea, Yemen's Security Belt forces said in a tweet on Sunday, in an attack witnesses said caused dozens of injuries or deaths.
No claim of responsibility was made.
The Security Belt forces are part of a southern separatist front in south Yemen, and are backed by the United Arab Emirates in a fight against Yemen's Iran-aligned Houthi group.
Witnesses told Reuters that a blast occurred near a guest platform during the parade and that dozens were injured or killed.
They reported seeing bodies at the scene.