Security forces are reviewing airport and public transport safety in cities worldwide.
The Brussels attacks also rekindled debate about security cooperation and police methods across Europe – and reignited debate about how to combat suicide bombers and gunmen.
About 300 Belgians are estimated to have fought with the Islamic State in Iraq and the Levant (ISIL, also known as ISIS) in the Middle East.
Belgium is the leading European exporter of fighters to foreign battlefields, which raises security concerns in neighbouring countries.
#BrusselsAttacks: Grief, Islam and double standards
So, how will the Belgian government and other European governments deal with the homegrown threat? And is a tougher security approach the answer?
Presenter: Folly Bah Thibault
Bruno Lete, Senior Officer for Foreign and Security Policy with the German Marshall Fund.
Mathieu Guidere, Professor of Islamic Studies at the University of Toulouse.
Ewen MacAskill, Defence and Intelligence Correspondent with The Guardian newspaper.
Source: Al Jazeera