Belgian police have arrested six people in Brussels as a major investigation continues into attacks that claimed 31 lives in the city on Tuesday.
The arrests were made in the Schaerbeek district. Separately, in France, a suspect who was plotting an attack has been arrested near Paris.
The Brussels bombings have been linked to last November’s Paris attacks.
US Secretary of State John Kerry, visiting Brussels, said that so-called Islamic State (IS) would be destroyed.
IS claimed the attacks in both Paris and Brussels.
Standing alongside the Belgian Prime Minister, Charles Michel, he expressed condolences for the victims and solidarity with Belgium, declaring “Je suis Bruxellois”.
The Western alliance would continue its fight to destroy IS, Mr Kerry said.
“We will not be intimidated. We will not be deterred.”
The arrests in Brussels were made late on Thursday, and followed house-to-house searches. Residents said they heard explosions during the police raids.
Belgian media reports on Friday suggest a seventh arrest has also been made in the Forest district of Brussels.
Also on Thursday evening, French police launched an anti-terrorism operation in Argenteuil, north-west of Paris, following the arrest hours earlier of a man suspected of planning an attack.
Interior Minister Bernard Cazeneuve said the suspected militant, a French national, was in an “advanced stage” of a plot.
The suspect, named as Reda Kriket, 34, was convicted in his absence by a Brussels court last year for recruiting IS members to go to Syria, officials say.
He was sentenced along with Abdelhamid Abaaoud, considered the main organiser of the Paris attacks and killed in a police raid in Paris days later.