The clip depicting a Renfe cargo train slowly travelling through a station loaded with around 50 armoured vehicles has been shared thousands of times on social media.
Some speculated that the army was preparing a response to imminent terrorist attacks based on secret intelligence.
"Something is about to happen and they are not telling us," was one comment, reported El Confidencial Digital.
"Something big is about to happen, the military are going to take the streets," said another.
Others dismissed the view that the tanks were a preventative measure against an imminent terror attacks and suggested the tanks might be preparing to invade Catalonia as the region embarks on an independence process.
In fact, El Confidencial Digital discovered that the footage was a hoax and that the convoy was transporting the "Castillejos II" cavalry brigade which had been mobilized for the NATO exercise held in Zaragoza earlier this month.
The footage therefore predated the Paris attacks in which 129 were killed and which have caused security measures to be reinforced across Europe.