The artillery on Tuesday bombarded gatherings of the mercenaries in Hudaydah province, a military official told Saba news agency.
The artillery hit the mercenaries in Mouthalath Jabalaih, located on the western coast, killing and injuring dozens of them, the report added.
Following the attack, ambulances rushed to the bombarded site, the official said.
Saudi Arabia and the UAE launched an offensive on June 13 to capture Hudaydah, the main entry point for food in a country teetering on the brink of famine.
The operation, however, came into an immediate halt in the face of stiff resistance by Houthi Ansarullah movement fighters and residents of the port city, which forced the kingdom to wind down the push.