Belgian police have used a water cannon to control several hundred rowdy protesters in central Brussels who ignored an official call for marches to be postponed following Tuesday's bombings.
Amid fears of further attacks, officials wanted to give police the scope to focus on investigations which have widened to other countries, with officers carrying out 13 new raids in Belgium itself.
Hundreds nevertheless gathered at the Bourse on Sunday to express solidarity with the victims of the suicide bomb attacks at Brussels airport and on a rush-hour metro train. Thirty one people were killed, including three attackers, and hundreds more injured, with Islamic State claiming responsibility.
Most of the protests were peaceful but white-helmeted riot police used the water cannon against a group of protesters, many of whom local media described as right-wing nationalists, who burst onto the square chanting and carrying banners denouncing Islamic State.
"It is highly inappropriate that protesters have disrupted the peaceful reflection at the Bourse [stock exchange]. I strongly condemn these disturbances," Prime Minister Charles Michel said, according to Belga news agency.
Brussels Mayor Yvan Mayeur said the group were "scoundrels".
In and around Brussels and Antwerp, police carried out 13 new raids in connection with the attacks, with nine people questioned and five later released, the prosecutor's office said.
With links to the Paris attacks in November becoming clearer, and amid criticism that Europe has not done enough to share intelligence about suspected Islamist militants, cooperation appeared to be deepening.
Belgian press agency Belga said on Sunday prosecutors had charged a man in connection with a raid in Paris on Thursday that authorities say foiled an apparent attack plot.
Belga named him as Abderamane A, who prosecutors had said on Saturday was being held after being shot in a raid in the Brussels district of Schaerbeek.
After a series of raids in Belgium and Germany, Italian police also arrested Algerian Djamal Eddine Ouali who is suspected of making documents for militants linked to the bombings in both Paris and Brussels. Authorities in Italy have confirmed he will be extradited to Belgium.
Germany's Federal Criminal Police Office was among the European security agencies still hunting for at least eight mostly French or Belgian suspects, Die Welt am Sonntag newspaper reported.
Belgian prosecutors also charged three men on Saturday including Faycal C, whom Belgian media identified as Faycal Cheffou and said he was "the man in the hat", as he has become known, in last Tuesday's airport CCTV footage that showed three men pushing baggage trolleys.
However, investigators have not confirmed that Cheffou is that man, a person close to the investigation told Reuters.
Officials said 24 victims from nine different nationalities had been identified so far from the attacks in Brussels, where the European Union and NATO have their headquarters. Fourteen were identified at the airport and 10 on the metro. A further four people remain unidentified.
In addition, 340 people were wounded, according to the latest official toll, of whom 101 are still in hospital, 62 of them in intensive care, many with severe burns.