The developments come after Hungarian Prime Minister Viktor Orban made it clear in mid-September that Budapest would not change its policy regarding illegal migration and would stand up to the European Union if needed.

Zoltan Kovacs, Hungary's Secretary of State for International Communications and Relations, has accused Belgian authorities of censorship with respect to opinions regarding migration-related issues.

In a video posted on his Facebook page, Kovacs explained that the Hungarian government had earlier arranged for a van to be driven through Brussels with a billboard promoting the idea that migration is connected with terrorist attacks.

READ MORE: Hungary Responds to UN, Rails It Will 'Never Be a Country of Migrants'

According to Kovacs, the truck was stopped by police on December 5 and the driver was arrested.

He underscored Budapest's right to express its opinion, arguing that the action was legal, which is why he said Brussels' meddling was unacceptable.

The billboard featured pictures of two deadly 2016 terrorist attacks in Europe: at Brussels' Zaventem airport and in the French city of Nice.

READ MORE: Not Welcome: Hungary Completes Second Border Fence to Block Migrants

Additionally, the billboard featured a picture of Belgian Member of the European Parliament Guy Verhofstadt, who has repeatedly criticized the migration-related policy of Hungarian Prime Minister Viktor Orban.

"Hundreds have died in terrorist attacks since 2015 but Guy Verhfstadt says: 'We don't have a migration crisis'. This is insane!" the message on the billboard read.

The developments came after Verhofstadt last month hired an advertising billboard van to drive around Brussels, in a move aimed at slamming Orban's policy. The billboard read: "First he [Orban] took our money, now he wants to destroy Europe."

READ MORE: Hungary Prepares 'Stop Soros' Bill to Criminalize Aiding Migrants

Hungary has long been critical of the EU's open-door policy, which is commonly alleged to have kicked off the continent's migration crisis . Budapest also opposes the EU's mandatory migrant relocation quotas.

Budapest's stance prompted the European Commission to launch its first infringement procedure against Hungary over its asylum legislation in December 2015. Hungary had set up fences and enhanced border control along its border with neighbouring Serbia.