Belgian police briefly used water cannon to control several hundred rowdy protesters in central Brussels today after the protesters ignored an official call for marches to be postponed following last 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 metro train.
31 people were killed, including three attackers, and hundreds more injured in the attacks. The so-called Islamic State claimed responsibility.
Most of today's protests were peaceful but 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.
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 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 said 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 yesterday.
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 yesterday including Faycal C., whom Belgian media identified as Faycal Cheffou.
Belgain media 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 said.
Dutch police arrest French national suspected of planning attack
Dutch police have arrested a 32-year-old French national in the port city of Rotterdam on suspicion of planning a terror attack, prosecutors said, in a raid carried out at the request of French authorities.
The 32-year-old man is thought to have been planning an attack in France in the name of the Islamic State group along with Reda Kriket, a terror suspect who was detained near Paris on Thursday, a French police source told AFP.
"French authorities on Friday requested the arrest of this French national," the Dutch prosecutor's office said in a statement, adding that the man was suspected "of preparing a terrorist attack".
The statement made no mention of any connection with the November attacks in Paris.
The detained French national is expected to be handed over to France "shortly", the statement added, a process that could take "several days", spokesman Wim de Bruin told AFP.