He has signed a one-year extension to his Rubin Kazan contract.
Azmoun has returned to Rubin Kazan after his loan spell with Rostov ends.
The Iranian forward had been already linked with Liverpool, Celtic, Sunderland and most recently Italian giant Lazio.
Azmoun scored 12 goals with three assists in 41 competitive games for Rostov this season, while he has 19 goals in 26 senior caps for Iran.
