Belgium is warning its citizens that there is “imminent” danger of an attack in the capital city of Brussels, following the November 13 attack on Paris that killed 130 people and injured hundreds more. 

Belgian police detained 21 people between Sunday night and midday Monday.

French President Francois Hollande is meeting with world leaders this week, including U.K. Prime Minister David Cameron, U.S. President Obama and Russian President Vladimir Putin, to discuss an escalation of strikes against ISIS and how best to counter international terrorism.

Here & Now security analyst Jim Walsh discusses this with host Indira Lakshmanan.