BRUSSELS -- U.S. Secretary of State John Kerry is holding counter-terrorism talks in Brussels on Friday as top members of Belgium's embattled government face ongoing criticism for a series of security and intelligence failings ahead of this week's bomb attacks in the city that killed 31 people and wounded 270.
Kerry's arrival Friday morning comes hours after least six people were detained in raids linked to Tuesday's attacks on the Brussels airport and subway system. Belgian prosecutors are expected Friday to decide whether to charge or release them.
As well as meeting with officials from Belgium and the European Union, which has its headquarters in Brussels, Kerry is due to pay his respects to the victims of this week's attacks, which he says underscore the urgent need for a unified front against the so-called Islamic State group.
Kerry, who landed at the still-closed Brussels airport, is set to meet with European Commission President Jean-Claude Juncker, Belgium Prime Minister Charles Michel and Foreign Minister Didier Reynders as well as Belgium's King Philippe.
Belgian lawmakers meanwhile are due to discuss how to beef up counterterrorism measures amid growing signs that Belgian authorities missed a series of signals pointing to a pending attack.
As the pressure on the government has mounted, Belgium's interior and justice ministers offered to resign Wednesday. However Prime Minister Michel refused to accept their resignations.
Authorities have formally linked the Brussels bombings and the Nov. 13 attacks that left 130 dead in Paris. Both were apparently carried out by the same Belgium-based Islamic State cell.
Some of the Brussels attackers had been on the run from authorities in France and Belgium but were still able to hide in safe houses, assemble bombs and carry out linked attacks.
Turkey announced this week that it had warned Belgium last year that one of the Brussels attackers, Ibrahim El Bakraoui, had been flagged as a "foreign terrorist fighter."
The intelligence shortcomings have prompted European authorities to call for quicker and more efficient intelligence cooperation.
A manhunt is underway for one of the Brussels airport attackers who was recorded on a surveillance video and had fled the scene. Prosecutors have not said how many attackers there were in total, or how many accomplices might be at large.
Belgian prosecutors said the raids Thursday night targeted central Brussels, Jette and the Schaerbeek neighborhood, where police had earlier found a huge stash of explosives and bomb-making material in an apartment used by the Brussels attackers.
Amid signs that life in Brussels was returning to some sort of normality on the third day of mourning the dead, authorities lowered Belgium's terror-threat level by one notch. However, they said the situation remained grave and another attack is "likely and possible." Belgium had been on its highest alert ever since Tuesday's bombings.
The Netherlands' foreign minister revealed Friday that three of the dead at the airport were Dutch citizens.
Foreign Minister Bert Koenders said the victims were a woman from the eastern city of Deventer and a brother and sister from the southern Limburg province who live in the United States. He did not release their identities.
Matthew Lee in Brussels and Mike Corder in The Hague contributed to this report.