"Through the group named Wagner, they are literally working as Haftar's mercenaries in Libya. You know who is paying them," Erdogan said, according to NTV.
"That is the case, and it would not be right for us to remain silent against all of this. We have done our best until now, and will continue to do so," he added.
Erdogan's comments come a day after Libya's internationally recognized government said it ratified a security and military accord between Ankara and Tripoli, opening the way for potential Turkish military help.
The Tripoli government is fighting a months-long offensive by Haftar's forces based in the country's east.