Belgian police calculate 45,000 people attended today's demonstration in Brussels, they have said on their official Twitter account.
The turnout was such that they had to change the route before the march started.
Under the slogan "Europe, wake up! Help Catalonia", the demonstration has exceeded the expectations of the organisers, ANC (Catalan National Assembly) and Òmnium Cultural, who predicted 20,000 attendees.
In a festive protest atmosphere, demonstrators showed up bearing Catalan flags, estelada "starred" pro-independence flags, EU flags and yellow scarves and ribbon loops. The colour yellow has become a symbol of solidarity with the Catalan leaders imprisoned for taking part in the organisation of the 1st October referendum.