A friendly-fire airstrike from the Saudi-led coalition in Yemen killed at least 20 fighters and wounded 20 others Saturday.
The incident happened while coalition forces in pursuit of Shiite Houthi rebels in southern Yemen struck a pro-government military encampment, military officials said.
The fighters had just forced out the Houthis from the encampment in Taiz province when the airstrikes hit them.
The coalition commanders on the ground have repeatedly complained about slow communication with military leaders in Riyadh, officials said.
Also Saturday, Saudi airstrikes left 13 Houthis dead in the desert province of Jawf.
The Saudi-led Arab coalition is backing forces loyal to the internationally recognized government of Yemen in its fight against Iran-backed rebels.
About 4,500 civilians have been killed in the conflict since March.