(Updates after start of match)
By Richard Martin
BARCELONA, Sept 13 Barcelona supporters displayed 30,000 pro-Catalan independence flags at the start of their Champions League game with Celtic at the Nou Camp on Tuesday, risking the wrath of European soccer's governing body UEFA.
The Champions League anthem was greeted by a cacophony of boos as it was played before kickoff.
The club were fined 30,000 euros ($34,000) after supporters waved the flags, known as esteladas, during the 2015 Champions League final in Berlin.
They were also fined 40,000 euros in October 2015 after fans brought the flags to their Champions League game against Bayer Leverkusen.
UEFA's Control, Ethics and Disciplinary Body ruled the club had breached their regulations, which prohibit "the use of gestures, words, objects or any other means to transmit any message that is not fit for a sports event, particularly messages that are of a political, ideological, religious, offensive or provocative nature".
The Court of Arbitration for Sport is currently studying the case following Barcelona's appeal.
Pro-independence groups including the National Catalan Assembly (ANC) distributed the flags before the game with Celtic, which came two days after Catalonia's national day.
Hundreds of thousands of people took part in a pro-independence march in Barcelona on the national day, Sept. 11, which was commemorated by the club, including president Josep Maria Bartomeu and captain Andres Iniesta.
As is customary at Barcelona home games, supporters chanted in favour of independence after 17 minutes and 14 seconds, marking the Siege of Barcelona in 1714.
Spanish police announced earlier this year that supporters would not be able to take the flags into the King's Cup final with Sevilla in May, although the ban was lifted on appeal. (Reporting by Richard Martin; Editing by Toby Davis and Clare Fallon)