Authorities have also asked that people do not update social media with sightings of police as they carry out raids.
So the people of Brussels have found a different way to respond to the frightening situation. With the power of lolcats.
Because, how can you be afraid in the face of cat dressed as a frog. Or a husky.
Or, you know, as a musketeer.
Even if the kitten is armed and apparently dangerous.
Or if they have studied the art of war.
And is actually pretty scary.
Or are being used by the authorities to track down suspects.
It's still a cat.
Take that, terror.
In fact, Belgian police were so impressed with Twitter users' work, they've issued a reward.
"For cats who helped us last night... Help yourself!"