The club from Kazakhstan killed a sheep last week at the Astana Arena the day before beating Celtic 2-0 in the playoffs.
In Glasgow ahead of Wednesday’s return match, Shakhter coach Viktor Kumykov suggested the ritual could be repeated.
UEFA says its competitions department wrote to inform Shakhter that animal slaughter “was not acceptable in or around our competitions,” and added that the Kazakh club “would face sanctions if it happens again.”
Shakhter, the lowest-ranked team remaining in the Champions League, is aiming to reach the 32-team group stage for the first time.
Viktor Kumykov, Shakhter Karagandy’s coach, said earlier this week that he had not ruled out slaughtering a sheep as part of a ritual ahead of the second-leg tie at Celtic Park.
Last Tuesday, Kumykov claimed that Shakhter sacrificed a sheep at Kazakhstan’s Astana Arena before a training session. The side went on to win 2-0 against Celtic.
But last night, the Scottish SPCA said animals could only be slaughtered in Scotland in licensed premises and has asked Celtic to confirm that no sheep are allowed into the ground.
Animal Concern Advice Line (Acal) has also written to Sir Stephen House, chief constable of Police Scotland, demanding that Mr Kumykov and his team are closely monitored during their stay in Scotland.
Speaking through an interpreter at a pre-match conference yesterday, Mr Kumykov said: “All I can say is that every team and every club has its own pre-match traditions and rituals. Celtic must have their own. We will try to respect our traditions and those traditions were in place even before we came to the club.”
Asked if the ritual would take place, he replied: “Possibly, yes.”
When asked where he planned to get the sheep, Mr Kumykov replied: “As far as we know in Scotland agriculture is very developed, so it shouldn’t be an issue to find a sheep.”
The Shakhter boss, however, played down the effects the pre-match ritual had had on the first game in Kazakhstan.
He said: “This tradition may have certain psychological impact on players that can help them to relax before the game.
“But obviously, what really matters is on the football pitch, the game and the final score and you know we scored twice in the first leg and Celtic failed to score, that’s what really matters.”
Mike Flynn, chief superintendent of the SSPCA, said: “There are strict rules on the transport and slaughter of animals in Scotland and it is only permitted in licensed premises.
“Killing a sheep in this way would be a criminal offence and anyone involved could face prosecution.
“We are seeking assurance from Celtic Park that no sheep will be allowed on the premises ahead of the match.”
Acal secretary John Robins wrote in his e-mail to Mr House: “I ask Police Scotland to closely monitor Mr Kumykov and his team during their stay in Scotland and if any attempt is made to repeat this superstitious nonsense and sacrifice a sheep, to immediately arrest all those involved and charge them.”
Animal rights group Peta wrote to the football governing body Uefa urging president Michel Platini to punish Shakhter after the sacrifice of a sheep before last week’s game.
Mimi Bekhechi, Peta associate director, said: “We are deeply disturbed that a sheep was stabbed to death in an attempt to bring good luck to the Kazakh team.
“We hope Mr Platini will agree that animal sacrifice has no place in modern society, and we hope the Uefa will act swiftly to ensure that the beautiful game is not further stained with the blood of animals.”
A spokeswoman for Police Scotland said: “Police Scotland has been working closely with the clubs. There will be no pre-match ritual which deviates from normal pre-match activity at any Scottish games.”
A spokesman for Celtic played down fears raised by the animal welfare charities. “Shakhter have told Celtic they do not wish this [sacrifice] to happen at all. They never had any intention of this happening at all,” he said.