Scottish club Celtic are to be investigated over "illicit chanting" by their supporters at the Europa League match at home to Stade Rennes earlier this month, European football's governing body said Monday.
"We would like to confirm that UEFA has opened disciplinary proceedings against Celtic for an incident of unsporting nature (illicit chanting)," UEFA said in a statement.
British media said the chanting may have referred to the Irish Republican Army (IRA). Celtic won the Group I match 3-1.
Scottish football is battling a long-running problem with sectarian chanting.