Barcelona: Spanish champions Barcelona face further sanctions from Uefa after thousands of separatist Catalan flags were flown at their Champions League opener against Celtic on Tuesday.

The Champions League anthem was drowned out by a chorus of boos and chants in favour of Catalan independence, while a large banner read: “Welcome to Catalonia.”

Barca were fined €150,000 (Dh618,521) by Uefa for the presence of the flags at the Camp Nou during last season’s competition, €50,000 of which was suspended for two years.

The club have previously stated their anger at the fines as “totally unjust and ... opposed to the exercise of the freedom of expression.”

The flag, known locally as the “Estelada”, which differentiates from the red and yellow Catalan flag by the presence of a five-pointed star within a blue triangle, has in recent years become a symbol of the independence movement within Catalonia.

Thousands of flags were distributed outside the ground by the Catalan National Assembly (ANC) to both sets of supporters before kick-off.

However, Uefa considers it a political symbol and fined Barcelona €40,000 after it was flown during a Champions League group game against Bayer Leverkusen last September.

The club was also fined €30,000 in July 2015 after it was flown during the Champions League final in Berlin the previous month, where Barca beat Juventus to lift the trophy.

Celtic have also fallen foul of Uefa’s intolerance for political symbols this season as they open disciplinary proceedings after a section of Celtic’s support displayed Palestine flags during a Champions League qualifier against Hapoel Beer-Sheva of Israel.