Right-wing protesters have gathered at a vigil for victims of Tuesday's Brussels attack, sparking confrontations and prompting a response from riot police.

Meanwhile, authorities in Italy have made another arrest in association with the ISIS-claimed attacks, which killed 31 and injured more than 300.

Brussels residents had originally been planning a "march against fear" on Sunday, but it was canceled after the minister of the interior made an appeal to the public. He said the police was stretched thin investigating the attacks and asked for the march to be called off, given security concerns. The planners of the march agreed.

But a vigil for victims was held at Brussels' city center, at the site where mourners have left flowers, candles and notes honoring the victims.

NPR's Melissa Block, reporting from the scene, described what it was like when the peaceful gathering was joined by a group of right-wing protesters.

"A group of right-wing extremists clad in black have marched to the center of this rally and have basically commandeered it. They have taken over," Melissa told our Newscast unit. "They're shouting, 'It's because of you,' meaning the migrants here in Brussels."

Melissa reported altercations between the extremists and the gathered mourners — then the arrival of Brussels police in riot gear.

"It looks like the police are coming in to clear the square and try to defuse this tense and potentially volatile situation," Melissa says.

Tensions have been high in the capital of Belgium this weekend.

A video posted on Islamic State-associated social media accounts on Saturday showed a Belgian militant speaking in Dutch and telling Belgium "the attack in Brussels is reaping what you had sown with your own hands," according to the SITE intelligence group.

"Just as you bomb the Muslims with your F15s, we will fight your people," the video continued.

In Italy, another arrest has been made in connection to the attacks. (Several arrests were made earlier this week, and multiple suspects have been charged. Three of the suspected suicide bombers have also been identified.)

The Associated Press reports on the new arrest:

"Italian police say they have arrested an Algerian man wanted by Belgian authorities for alleged involvement in a Belgium-based network of false IDs used by suspects implicated in the Paris and Brussels attacks."The man, arrested near Salerno, came to Italy's attention by applying for a residency permit. Police Sunday noted he had the same name of man sought by Belgium for alleged involvement in 'a criminal network dedicated to false documents on a large scale' that emerged last year in Brussels."Belgium issued a warrant in January, three months after a raid in the Brussels suburb of Saint-Gilles yield about a 1,000 digital images used for false documents."Police are investigating why the man was in Italy and expect extradition procedures to begin. They didn't identify the man or specify when he was arrested."

Belgian prosecutors have also brought charges against a second man accused of involvement in a plot to attack Paris. Police are continuing to conduct raids in Brussels and elsewhere in Belgium.

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