Prosecutors announced a direct connection between the Brussels bombings that killed 31 people and injured 270 others and last year's attacks on Paris, which appear to have been carried out by the same Islamic State network. The attacks have laid bare European security failings and prompted calls for better intelligence cooperation.
PHOTOS: Paris bombmaker among dead in Brussels attack
Interior Minister Jan Jambon said after a government meeting Thursday that "If you put all things in a row, you can ask yourself major questions" about the government's handling of the threat from Islamic extremists.
Notable among the questions is those raised by Turkey's announcement that it had warned Belgium last year that one of the Brussels attackers had been flagged as a "foreign terrorist fighter."
But the prime minister asked Jambon and Justice Minister Koen Geens to stay on, given the current challenge the government is facing. The country is under its highest terror alert level.
The meeting came as Belgian and French media reported a second attacker is suspected of taking part in the bombing this week of a Brussels subway train and may be at large.
PHOTOS: Explosions rock Brussels, Terror attacks kill dozens
Belgian prosecutors have said at least four people were involved in Tuesday's attacks on the Brussels airport and a subway train, including brothers Ibrahim and Khalid El Bakraoui, identified as suicide bombers. European security officials identified another suicide bomber as Najim Laachraoui, a suspected bombmaker for the Paris attacks.
Khalid El Bakraoui blew himself up on the train, while Ibrahim El Bakraoui and Laachraoui died in the airport.
Prosecutors have said another suspected participant in the airport attack is at large, a man in a hat seen in surveillance images who has not been publicly identified.
Belgian state broadcaster RTBF and France's Le Monde and BFM television reported Thursday that a fifth attacker may also be at large: a man filmed by surveillance cameras in the Brussels metro on Tuesday carrying a large bag alongside Khalid El Bakraoui. It is not clear whether that man was killed in the attack.
Prosecutors, who have not said how many people overall may have taken part in the bombings, did not respond to the reports.
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The federal prosecutors' office issued a statement Thursday saying that Khalid El Bakraoui had rented a house used as a hideout for the Paris attackers, and that he had been hunted by police since December.
Several of the Paris attackers were Belgian or had links to Belgium, and the country has been on high alert for possible attacks.
Turkey's president said Wednesday that one of the Brussels suicide bombers, Ibrahim El Bakraoui, was caught in June 2015 near Turkey's border with Syria and deported to the Netherlands, with Ankara warning Dutch and Belgian officials that he was a "foreign terrorist fighter." Turkish officials said he was later released from Dutch custody due to lack of evidence of involvement in extremism.
European Union justice and interior ministers were holding an emergency Thursday afternoon to discuss the attacks, and French President Francois Hollande said France would "speak loud and clear" for better intelligence sharing and tougher measures against weapons trafficking.
Also Thursday, the chief suspect in the Paris attacks, Salah Abdeslam, was summoned to court in Brussels after his arrest last week in the Belgian capital. His lawyer, who had initially vowed to fight extradition, said Abdeslam now wants to be sent to France as soon as possible.
Abdeslam evaded police in two countries for four months before Friday's capture, and the attackers in Brussels may have rushed their plot because they felt authorities closing in. Abdeslam's lawyer, Sven Mary, told reporters at the courthouse that he asked for a one-month delay on any transfer while he studies the large dossier, but that Abdeslam "wants to explain himself in France, so it's a good thing." Mary said the extradition process should be done by mid-April.
France is seeking Abdeslam's extradition to face justice for his involvement in the Nov. 13 attacks on a Paris rock concert, stadium and cafes, which killed 130 people. Several attackers were also killed.
Belgium is holding three days of national mourning.
Belgian Prime Minister Charles Michel, in a speech Thursday, said the attacks on the European Union's capital targeted the "liberty of daily life" and "the liberty upon which the European project was built."
"Our country and our population were hit at its heart," he said in front of the Parliament building. He honored the "children who have lost their papas, who have lost their mamas" in the attacks.
Security remains tight, but barriers were removed around the subway station hit by the attack, Maelbeek. The airport will remain closed until at least Saturday.
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Associated Press reporters Raf Casert and Angela Charlton in Brussels contributed to this report.
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