Celtic will next month face disciplinary action from UEFA over "illicit chanting'' in the Europa League win over Rennes at Parkhead, European football's governing body has confirmed.
A spokesperson for UEFA said that Celtic will on December 8 be called before the organisation's control and disciplinary body to face a charge of an incident of an unsporting nature, namely illicit chanting, during the 3-1 defeat of the French side on November 3.
Celtic had already confirmed they were "looking into the claims'', which are believed to centre on songs about the IRA.
Possible UEFA sanctions include a fine and ban on supporters, although Celtic have not been punished for a similar offence before.
The Scottish giants are understood to have been taken by surprise by the action, with sources suggesting no issues were raised during or immediately after the match.
It is believed Strathclyde Police made the UEFA delegate aware of "offensive'' singing during the encounter. Celtic last month urged fans to stop singing pro-IRA chants after being "inundated'' with complaints from their own supporters following their 2-0 defeat by Hearts at Tynecastle.
Lothian and Borders Police announced they had launched an investigation into the "singing of sectarian songs'' following the Scottish Premier League game on October 2.
Celtic's city rivals Rangers have been punished for similar offences in the past. Rangers fans were banned from travelling to their next away game in Europe and the club were fined more than £70,000 after being found guilty of two counts of "discriminatory behaviour'' on the part of their fans in April following Europa League games against PSV Eindhoven.
Rangers were also handed a suspended ban on a second away game and warned they faced playing a home game behind closed doors if found guilty of the same offence within three years.
The Ibrox club had received fines following similar incidents in matches against Villarreal and Osasuna in recent years.