The Turkish transfer window does not close until Friday, the BBC cited a source close to the negotiations as saying talks continue, though a deal maybe unlikely at this point.

Multiple reports earlier on Thursday quoted Fener coach Aykut Kocaman as saying the two sides were still not close to an agreement.

"We were really close to sign[ing] Diego Costa but now we seem far away," Kocaman said. "The talks between the two clubs were going really well. But here we are."

Costa has yet to rejoin Chelsea after being told last season the club will not stand in the way of him leaving.

But Costa has said he wants to join Atletico Madrid, who can not sign him until January because of a transfer ban.

Also on Thursday, Atletico president Enrique Cerezo denied that this week's surprise contract extension for coach Diego Simeone was connected to Costa returning to the club.