Concise News understands that the Turin side confirmed this on Tuesday morning after Aina, 22, spent the last term on loan.
According to Torino president, Urbano Cairo, the club have exercised their option to buy Aina with the defender’s present deal set to elapse at end of June.
“We exercised our option to buy Ola Aina, as well as [Christian] Ansaldi and [Koffi] Djidji,” he said.
“Now Torino own all their players.”
Aina earned eight caps for the Super Eagles side and is part of the team to the 2019 Africa Cup of Nations.