Belgian police briefly used water cannon to control several hundred rowdy protesters in central Brussels on Sunday after they 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, leading to the arrest of an Algerian in Italy and intelligence cooperation with Germany. Police carried out 13 new raids in Belgium itself.
Hundreds nevertheless gathered at the Bourse 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. Islamic State has claimed 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, Italian media said on Saturday.
His name was found in documents in a raid on an apartment near Brussels last October, including some with photos of militants involved in the attacks in Paris and in Brussels and the aliases they used.
WEB OF LINKS
As the web of links between the suspects and attacks emerges, German lawmakers said Europe urgently needed to improve the way its security agencies shared information.
But 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. They are thought to be on the run in Syria or Europe.
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.
A video posted on social media outlets used by Islamic State on Saturday showed a Belgian militant in the group's de facto capital Raqqa, Syria, taunting his home country in Flemish.
"You learned nothing from the lessons of Paris, because you continued fighting Islam and the Muslims. For this I want to tell you that the attack in Brussels is reaping what you had sown with your own hands," Hicham Chaib, whose nom de guerre was given as Abu Hanifa al-Beljiki, said.
"Just as you bomb the Muslims with your F-16s, we will fight your people."
The authenticity of the video could not immediately be verified by 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 on Saturday, of whom 101 are still in hospital, 62 of them in intensive care, many with severe burns.
Away from the protests on the Bourse square, Brussels was largely quiet on Sunday, with many celebrating Easter but Monseigneur Jozef De Kesel, archbishop of Brussels, told Reuters it would be difficult to celebrate as usual.
"The foundations of our society, freedom, respect for others, have been hit, attacked," he said.