Manchester United, Arsenal, Southampton and Atletico Madrid watched Celtic forward Moussa Dembele during Wednesday's Champions League match against Barcelona.

Dembele has been a revelation for Celtic this season, scoring 16 goals in 26 games in all competitions.

United and Arsenal have been long-term admirers of Dembele and have watched him on several occasions this season.

Celtic are desperate to retain Dembele and are unlikely to consider a sale during the January window.