A post on the La Liga club's account at 5.30am today contained a video of Messi scoring against Los Blancos alongside the message: "Benvingut Messi! Bienvenido Messi! Welcome Messi! Bienvenue Messi! #Messi."
The hacking group OurMine later claimed responsibility for the hack, explaining: "Internet security is shit and we proved that."
The bogus tweet remained online on Madrid's Spanish and English-language accounts for around 90 minutes before being removed.