Cracks within the anti-Houthi bloc have widened over the past several months.
Footage circulated online of Sunday's attack showed a hole in a stage at the edge of the field, apparently from an explosion, while other footage showed bodies on the ground.
More than 21 people, including civilians, were injured in the blast, al-Shoebi said, blaming the Houthis for the attack.
The rebel group did not immediately comment.
The Houthis have been trying to wrest Dhale province from the southern separatists for years, but without much progress.
The conflict in Yemen began with the 2014 takeover of Sanaa by the Houthi rebels. They drove out the government of President Abed Rabbo Mansour Hadi, forcing him to flee to the south and eventually to Saudi Arabia, which entered the war in 2015.
The fighting in the Arab world's poorest country has killed more than 100,000 people and left millions suffering from food and medical shortages.
The conflict has also pushed the country to the brink of famine.
- AP