Police have cleared crowds of self-proclaimed "hooligans" from a makeshift memorial site for the victims of the recent triple bombing attack in Brussels, the Belga news agency reported, while adding that there was still a high security presence.
Belgian Prime Minister Charles Michel had called for calm after around 450 black-clad football supporters - some hooded and apparently drunk - gathered in central Brussels chanting "Belgian hooligans, we are at home," the agency said.
Reported to have come from the town of Vilvoorde, north of Brussels, the protesters gathered at the square outside the former stock exchange in Brussels, despite calls by authorities not to hold any demonstrations in the wake of the attacks.
Police had earlier encircled the crowd on the square, then pushed them back to a nearby train station, where they were put on trains heading back north.
Around 10 people have so far been taken into custody, Belga reported.
The hooligans vandalized public property and threw trash cans along the way, while hitting police with projectiles, Belga reported. Two police officers were slightly injured. Other people booed and applauded as the hooligans were pushed back, according to the agency.
The hooligans, who have links to different football clubs, had arranged to meet in Vilvoorde before heading into Brussels, officials told Belga. Some were also reported to have made fascist salutes during their protest.
The state broadcaster RTBF quoted witnesses as saying that some of those present appeared to be far-right activists.
One man at the scene described the atmosphere as "very aggressive." He added that the crowds dressed in black were facing off with a more colourful bloc of pro-diversity demonstrators.
Michel had asked people in the Belgian capital "to keep their cool and to stay calm" in the face of the unauthorized protests.
Calling for the respect for those mourning the loss of life in Tuesday's terrorist attacks, the premier condemned the impromptu demonstration, saying "it is completely inappropriate that protesters interrupt [the period of] contemplation at the Bourse. ... People are gathering to find comfort."
Meanwhile, officials raised the death toll in Tuesday's terrorist attacks to 31 victims. They also indicated the total was actually higher because further victims had also died in hospital, but could not yet say how many.
On Saturday, officials had revised the number of victims down to 28 and said the previously reported figure of 31 dead had included three attackers. Sunday's figure of 31 reflected only victims.
Earlier Sunday, police in Belgium carried out 13 terrorism-related raids in Brussels neighbourhoods and near the northern city of Antwerp, prosecutors said in a statement.
Nine people were taken into custody for questioning, with five of them released by the afternoon.
The raids were carried out in connection with a "terrorism file," the prosecutors added, without specifying which case.
Germany's Die Welt newspaper reported that European security authorities are searching for at least eight further suspects linked to attacks carried out by Islamic State-affiliated terrorists in Paris and Brussels.
The Islamists, mostly French and Belgian, are believed to be on the run in Syria or within Europe, the newspaper reported, citing security sources.
The terrorist attacks in Paris on November 13 left 130 people dead, while the most recent attacks on March 22 in Brussels left 31 people dead.
It was unclear whether the reported suspects were among those arrested in Belgium on Sunday.