The mayor of the Brussels district of Anderlecht banned both the “European Dissidence Congress” and protests against it on security grounds.
The organisers – a Brussels bookshop and the Debout les Belges (Belgians, Rise Up) group – had kept the venue secret until as late as possible to try to dodge a ban.
Guests included Dieudonné M’Bala M’Bala, whose latest tour was banned on the grounds of anti-Semitism, Kémi Seba, the former leader of the violent anti-Semitic group Tribu Ka, and Alain Soral, a former Communist who has become a far-right theoretician.
The Belgian League against anti-Semitism, LBCA, on Friday filed a complaint against "a day of hate, that would serve as a platform for the worst gathering of anti-Semite authors, theorists and propagandists that our country has seen since the end of World War II".
The Nazi-hunting Simon Wiesenthal Centre joined calls for a ban, dubbing the event an "anti-Semitic Hatefest".
"The fact that this hatefest is to be held in Brussels, the capital of Europe, the seat of its Parliament... is a threat to democracy reminiscent of the 1920s Weimar Republic, which brought Europe to the Nazi abyss," the centre's director for international relations Shimon Samuels said in a statement.
Debout les Belges leader Laurent Louis said he would defy the ban, saying that the guests have “confirmed they are coming”.
"Do not give in to pressure and come with your families, in calm and good spirits," he wrote on his Facebook page.