Police are following a positive line of inquiry over the attempted murder of a man following an Old Firm match.
Three men, aged 29, 30 and 47, were taken to Glasgow Royal Infirmary with serious injuries after an incident in the Merchant City at around 5pm on Sunday.
Officers were called to the scene in Blackfriars Street following reports of an altercation, which appear to have involved weapons of some kind.
It came after Celtic beat Rangers 2-1 following a late winner from James Forrest.
The 47-year-old sustained very serious injuries in this attack and is still in a critical conditionDetective Inspector Peter Crombie
Police are treating the attack on the 47-year-old, who is in a critical condition, as attempted murder and the attacks on the other two men as serious assaults.
The 29-year-old and 30-year-old have since been released from hospital.
Officers are appealing for information and asked anyone with footage of the incident to contact them.
Detective Inspector Peter Crombie said: “The 47-year-old sustained very serious injuries in this attack and is still in a critical condition. His family are distraught.
“We are doing everything we can and are particularly looking for mobile phone footage of the incident as it could be the crucial piece in this investigation.
“You may think that someone else will have got in contact so you don’t have to, this is not the case and we need to speak to everyone who was there that evening and witnessed this incident.”