"For the cats that helped us last night... Help yourselves!" Belgian police said on their Twitter account, with a photo of a metal bowl with the police logo in French and Flemish, filled with cat food pellets.
It was retweeted more than 4,400 times in French and 1,400 times in Flemish.
The Twitter hashtag #BrusselsLockdown went viral last night when social media users posted pictures of their feline friends -- a light-hearted response to an official request from police not to put information about their operation on the Internet.
The cat photos were a whimsical break from a tense situation, with Brussels under security lockdown since Saturday morning after the government said there was a "serious and imminent threat" of attacks like those in Paris on November 13.
Key Paris suspect Salah Abdeslam, who is believed to be in Belgium, remains at large despite police arresting 21 people overnight.
