Belgian police asked people not to tweet details of their operations hunting the Paris killers, but they did ask for Twitter users to 'support' the hashtag #BrusselsLockdown.
In a bizarre twist, the hashtag went viral as Belgians used it to post pictures of their cats.
Belgium's capital city was in lockdown for a third day and what is normally a vibrant and bustling place to be at this time of year, the streets were deserted as police hunted people for the Paris massacre which killed 130 people on November.
Instead of taking pictures of what they could see or describing police operations, Belgians posted pictures of cats.
As the theme caught on, some posted photos of cats looking suspicious, others of cats looking scared.
Afterwards Belgian authorities thanked the internet.
'The federal prosecutor and the police services must thank the press and social media users for taking into account the needs of the ongoing operation,' prosecutors' office spokesman Eric Van Der Sypt told a press conference as he announced 16 arrests.
