Story highlights Belgium's capital has been placed under the highest level of terror alert

Authorities ask people not to tweet about police movements; they respond with cat pics

The lighthearted response to their situation drew admiration from around the world

(CNN) This weekend, Belgians were confronted with the sober reality that their capital has been placed under the highest level of terror alert, due to an unspecified "serious and imminent threat."

The city's schools, universities and subway system remain closed Monday as authorities scramble to locate individuals they fear could be planning Paris-style attacks on Brussels, the country's capital and home of the main seat of the European Parliament.

But rather than give in to fear, Belgians have responded on social media with a defiant sense of whimsy. And cat pictures -- lots and lots of cat pictures.

The stream of cat pics was sparked when the country's federal police made a request on Twitter for the public to maintain silence about the ongoing counter-terror operations on social media, for fear of alerting potential targets of the raids to police movements.

Par sécurité, veuillez respecter le silence radio sur les médias sociaux concernant les opérations de police en cours à #Bruxelles. Merci — Police Fédérale (@PolFed_presse) November 22, 2015

Twitter users flooded the hashtag #BrusselsLockdown with cat memes, in a powerful gesture that showed they wouldn't lose their sense of humor over the terror threat -- and effectively buried any legitimate intelligence on police movements that might have been shared.