A sea of around 45,000 pro-Catalonia protesters demonstrated in Brussels on Thursday to show support for the region's deposed president Carles Puigdemont and urge the European Union to support its drive for independence from Spain.

Demonstrators chanted “Wake up Europe!” and waved Catalonia's red, yellow and blue Estelada separatist flag as they marched past the European Union headquarters in the Belgian capital.

“We cannot abandon our president, who is in exile here,” Antoni Llenas, 59, a protester wearing a flag over his shoulders, told AFP. “We are here to continue the struggle for our independence and to ask for the freedom of our political prisoners.”

Belgian police said on Twitter that there were an estimated 45,000 protesters, more than double the 20,000 that organisers said they originally expected. The rally began peacefully, according to AFP reporters on the scene.

Puigdemont and four former ministers fled to Brussels in November, saying they wanted to take their cause to the European level after Spain charged them with sedition and rebellion over Catalonia's independence referendum in October.

On Monday, the Spanish government dropped a European arrest warrant for the five, but Puigdemont said he would stay put for now as they still face arrest in Spain if they return for regional polls in Catalonia that Madrid has called for December 21.

Protesters arrived in a stream of coaches and camper vans with Spanish registration plates, and gathered in the Cinquantenaire Park in the city's European quarter before the start of the march at 10:30 GMT.

Children and families were among those who began the march in high spirits despite the cold and rain.

Their route is taking them past the headquarters of the European Commission and they will end up in a square between the European Council and European Parliament.

The EU has strongly backed the Spanish government over the Catalan issue, saying that it is an internal matter for Madrid.