BRUSSELS -- Heavily armed police swept into Brussels neighbourhoods Friday in operations linked to this week's bombings as well as a suspected new plot in France, detaining three people and shooting two of them in the leg. One man was carrying a suspicious bag while accompanied by a young girl.

As Easter weekend began, jittery Europeans faced uncertainly about how many violent extremists remain at large, and where and when they might strike again.

On Friday afternoon, two blasts and gunfire rang out in the Schaerbeek district of Belgium's capital, where police earlier found explosives and bomb-making material in an apartment used by the suicide attackers who killed 31 people and wounded 270 in assaults on the Brussels airport and subway.

Authorities, meanwhile, confirmed one of the attackers at the airport was the bomb-maker who made explosive vests used in last year's carnage in Paris -- the most definitive link yet between the two attacks, both of which have been claimed by the Islamic State group.

On the third and final day of national mourning, U.S. Secretary of State John Kerry laid a wreath at the airport for the victims of Tuesday's bombings -- a ceremony that was skipped by Belgian Prime Minister Charles Michel because of the police operations.

Kerry, in a hastily arranged visit, defended Belgium's counterterrorism efforts despite a series of security and intelligence failures before the bombings that have brought sharp criticism of top members of Belgium's embattled government. Authorities believe both the Brussels attacks and the Nov. 13 bombings in Paris that killed 130 people were plotted from Belgium.

Confirming that several FBI agents are involved in the investigation, Kerry said the "carping" about Belgium's shortcomings "is a little bit frantic and inappropriate."

He also lashed out at the Islamic State group. "We will not be deterred," he said. "We will come back with greater resolve -- with greater strength -- and we will not rest until we have eliminated your nihilistic beliefs and cowardice from the face of the Earth."

As the identities of the victims began to be made public, officials announced that American, British, German, Chinese, Italian, French and Dutch citizens were among the dead.

A manhunt has been underway for one of the airport attackers who was recorded on a surveillance video and fled the scene. Prosecutors have not said how many attackers there were in total, or how many accomplices might be at large.

But they said Friday that DNA analysis and an official investigation had confirmed one of the suicide bombers at the airport was Najim Laachraoui, 24, a suspected bomb-maker whose DNA was also found on a suicide vest and bomb used in the Paris attacks. European security officials had earlier in the week confirmed his identity to The Associated Press, thus linking the Brussels and Paris bloodshed.

On Friday, dozens of heavily armed officers swept into Brussels' Schaerbeek neighbourhood, as well as the Forest and Saint-Gilles districts, the Belgian federal prosecutor's office said. It was the second such raid in Schaerbeek in two days.

Officers began the operation about 1:30 p.m., when "two big explosions" echoed through Schaerbeek, resident Marie-Pierre Bouvez told the AP, and it lasted about two hours. It was not immediately clear if the blasts were controlled explosions.

Bouvez said police kept the area locked down and shouted at her to "get back inside" when she tried to go into the street.

At a tram stop, a man sitting with a young girl and holding a bag was ordered by police "to put the bag far from him," and after he did so, police shot him twice, hitting him in the leg, said Norman Kabir, a local electrician. The girl was taken into safe custody, and a bomb-squad robot searched the bag, he added.

State broadcaster RTBF said police apparently feared the bag held explosives.

Schaerbeek district Mayor Bernard Clerfayt told RTBF the raid was linked to the Brussels attacks as well as Thursday's detention in France of a man authorities said was in the advanced stages of plotting a new attack.

The 34-year-old suspect, Reda Kriket, has a past Belgian terrorism conviction and was linked to the suspected ringleader of the Paris attacks, Abdelhamid Abaaoud, officials told the AP.

Meanwhile, the top suspect in the Paris bombings, Salah Abdeslam, who was captured in Brussels one week ago, has stopped co-operating with police and "no longer wants to talk," said Justice Minister Koen Geens. Abdeslam exercised his right to silence during the second of two rounds of questioning on March 19, prosecutors said. France is seeking his extradition, and his lawyer said he is prepared to go.

Elsewhere, Belgium's nuclear agency said it has withdrawn the entry badges of some staff and denied access to other people recently amid concern the nuclear plants could be a target.

Immediately after Tuesday's attacks, security was boosted around Belgium's nuclear sites, and hundreds of workers were sent home.

Last month, authorities said searches after the Paris attacks uncovered video linked to a person working in Belgium's nuclear industry.

Belgian media reported this week that two of the suicide bombers in the Brussels attacks, brothers Ibrahim and Khalid El Bakraoui, had video of the home of a senior official at the Mol nuclear waste facility in the Flanders region.

In the neighbourhood of Molenbeek, home to some who took part in the Paris attacks, Sheik Mohamed Tojgani denounced the Brussels bombers during a sermon before Friday prayers.

"Terrorism is terrorism," said Tojgani, the imam of Molenbeek's main mosque. "It has no state, no nationality, no religion, no country."

In a message to the Belgian people, he added: "You are from us and we are from you. What affects you, affects us."

Poignant accounts of some of the victims' last moments also emerged Friday.

Among them was Liberian-born Elita Borbor Weah, seen smiling in a photo she texted to her family shortly before the blasts at the Brussels airport. Wearing a black coat and a white-and-black checked head-covering the 40-year-old mother of a teenage daughter is seen standing in the departure lounge.

She was on her way to Rhode Island for her stepfather's funeral when she was killed, her tearful brother, Oscar Weah, told the AP.

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Associated Press writers Angela Charlton, Thomas Adamson, Mark Carlson and Matthew Lee in Brussels, Lori Hinnant in Paris and Mike Corder in The Hague contributed to this report.