Brussels (AFP) - Belgian riot police fired water cannon to disperse far-right football hooligans who disrupted mourners at a shrine for victims of the Brussels attacks, as police arrested several suspects in a series of new raids.

In scenes that compounded a week of grief for Belgians, black-clad protesters shouting anti-immigrant slogans moved in on the makeshift memorial at Place de la Bourse where hundreds of people had gathered in a show of solidarity.

Under-fire Belgian authorities meanwhile detained four terror suspects after carrying out 13 raids as they seek to round up a web of jihadists with links to the carnage in the Belgian capital and to attacks and plots in France.

The clashes between the far-right demonstrators and police underscored the tensions in Belgium after Tuesday's Islamic State suicide attacks on the airport and the metro system in which 31 people died and 340 were wounded.

"This is our home" and "The state, Daesh accomplice" around 300 hooligans chanted, using an alternate term for IS, as they gathered near the square by the stock exchange building, AFP journalists witnessed.

Some trampled on the carpet of flowers, candles and messages left at the site by mourners in recent days while at least one wore a mask with a well-known far-right symbol.

Police urged the mourners, who included some Muslims, not to provoke the hooligans, but some chanted "Fascists! Fascists! We're not having it!"

Riot police with helmets and shields corralled the hooligans before dispersing them with high power water jets, and marshalling them onto trains out of the city.

Around 10 people were arrested, police told AFP.

The mourners gathered despite the fact that organisers had earlier called off a "March Against Fear" in Brussels on Easter Sunday at the request of Belgian authorities, who said police needed the resources for the attacks investigation.

- Death toll rises -

Meanwhile, the Belgian Crisis Centre said 31 people had died in the airport and metro attacks, up from an earlier toll of 28. The figure does not include the three suicide bombers.

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All but three of the victims have now been identified, it said.

According to an earlier statement, a total of 340 people from 19 countries were wounded, of whom 101 remain in hospital -- 62 of them in intensive care.

The US State Department on Sunday confirmed the death of two more Americans, bringing the total to four.

As Belgium struggles to come to terms with the tragedy, recriminations continue over whether the authorities could and should have done more to prevent the carnage, as the links to the November Paris attacks by IS grow clearer by the day.

Police carried out 13 raids Sunday across Brussels and the towns of Duffel and Mechelen to the north, the federal prosecutor said, questioning nine people and holding four for further inquiries.

In the latest piece in the puzzle of the jihadist cross-border networks, police arrested a 32-year-old French national in Rotterdam Sunday on suspicion of planning a terror attack, Dutch prosecutors said, following a raid carried out at the request of French authorities.

The 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.

Belgian prosecutors at the weekend also charged two men with involvement in a terror group over the foiled plot to attack France.

- 'Molenbeek in France' -

French minister for cities Patrick Kanner on Saturday sparked debate by claiming that "around a hundred neighbourhoods" in France could be compared to Molenbeek, the gritty Brussels district which has been home to several jihadis.

"We know that there are today around a hundred neighbourhoods in France which have potential similarities to what has happened in Molenbeek," he said during a radio interview, though some in his own Socialist Party questioned the statement.

Also on Saturday, a Belgian suspect identified as Faycal Cheffou, widely thought to be the fugitive third bomber from the airport, was charged in Brussels with terrorist murder and participation in a terrorist group.

There has been intense speculation he is the man wearing a dark hat and light-coloured jacket seen in airport surveillance footage alongside Ibrahim El Bakraoui and Najim Laachraoui who blew themselves up.

Brussels Airport said it would carry out a test run on Tuesday to see if the repair work in the wrecked departure hall was satisfactory, but it could not give a firm date for resuming services.