Brussels: The Belgian capital was locked down for a second day on Sunday with police and troops on the streets as authorities reviewed whether to extend a security alert meant to prevent a repeat of the bloody Paris attacks.
With the world on edge over the jihadist threat, US President Barack Obama said the most powerful tool to fight the Islamic State extremist group was to say "that we are not afraid".
In Paris, Defence Minister Jean-Yves Le Drian said a chemical or biological attack "was among the risks" faced but that all possible precautions had been taken.
Belgian officials were due to meet later today to review the security alert in Brussels, imposed over fears jihadists were plotting similar attacks to those in Paris which left 130 people dead on November 13.
The city's metro system and public buildings were closed, with shops and restaurants following suit after the terror alert was raised to the highest level of four because of what officials said yesterday was an "imminent threat."
Central Brussels, usually bustling, was virtually deserted, with police and troops on patrol.
Interior Minister Jan Jambon said the authorities were looking not just for Paris suspect Salah Abdeslam who managed to slip past French security forces after the carnage in the City of Light.
He warned that the capture of Abdeslam, a Belgian-born 26-year-old whose brother Brahim blew himself up at a cafe in Paris, would not in itself end the threat.
"It involves several suspects and that is why we have put in place such exceptional measures," the Belga news agency cited Jambon as telling Flemish television.
Justice Minister Koen Geens said in a separate Belga report he expected the metro to re-open on Monday "if all passes off normally... We are not going to paralyse Brussels economically."
Belgium and the capital, home to the European Union and NATO, are no strangers to Islamist violence.
Four people were shot dead at the Brussels Jewish museum last year, and in January security forces killed two suspects linked to the Charlie Hebdo killings in Paris.
The UN Security Council on Friday authorised nations to "take all necessary measures" to fight jihadist violence after a wave of attacks, including the downing of a Russian aircraft in Egypt with the loss of 224 lives and the storming of a luxury hotel in Mali which left 19 dead.