Celtic have warned supporters that a section of Celtic Park could be closed after Uefa opened disciplinary proceedings against the club.
Issues with fans' behaviour came to a head during Tuesday's Champions League qualifying round win over Northern Ireland's Cliftonville, when supporters let off fireworks in the stadium.
The Scottish Premier League champions have expressed concern regarding both overcrowding in Section 111 of their Glasgow home and fans' refusal to comply with the wishes of safety stewards on match days, as well as 'moshing' and 'body surfing'.
A statement read: "The directors and board of Celtic Football Club are responsible for the safety of all supporters, and this is their primary objective.
"For some time the club has been under close scrutiny by the Glasgow City Council Safety Advisory Group with regard to serious safety concerns within Section 111.
"The club is keen to work with spectators in Section 111 to resolve safety concerns. However, it should be understood that failure to stop this unsafe behaviour will require the closure of this area in Celtic Park.
"The club recognises the many examples of good support for the team emanating from this part of the ground and in particular the efforts of the ‘Green Brigade’ in organising positive displays which are commended. However, the unsafe aspects of spectator behaviour in Section 111 require to be addressed with immediate effect.
"The directors and board of Celtic Football Club consider their responsibilities with regard to spectator safety to be of paramount importance. We will continue dialogue with representative of fans in this area to resolve these serious safety concerns however this unsafe behaviour must stop."
Celtic have previously faced scrutiny from Uefa over allegations of sectarian chanting, which saw them hit with a £12,700 fine in December 2011.