Celtic manager Ronny Deila insists Virgil van Dijk does not want to leave the Scottish Premiership leaders in January.
Celtic boss Ronny Deila says keeping his best players will take priority over acquisitions in the transfer window.
Club captain Gaby Zakuani is among four Peterborough players to be fined and transfer-listed following a breach of club discipline, the npower Championship club have announced.
Record signing Tyrone Barnett and fellow forwards Nathaniel Mendez-Laing and Emile Sinclair are the other players to be punished following an internal inquiry.
A statement on Peterborough's official website said: "Peterborough United are disappointed to report that Gabriel Zakuani, Nathaniel Mendez-Laing, Emile Sinclair and Tyrone Barnett have been transfer-listed and fined by the football club following an internal investigation into a breach of club discipline.
"The club will be making no further comment on the matter."
Centre-half Zakuani has made over 150 appearances in four years at the club but appears unlikely to continue in his role as captain.
Barnett and Sinclair both signed for Posh last season in big-money moves from Crawley and Macclesfield respectively, while winger Mendez-Laing only arrived from Championship rivals Wolves in the summer.