Anti-terror police swooped on the French city of Lyon last night just days ahead of the official start of Euro 2016 in France .
Emergency responders took part in a mock terror training exercise as travelling fans were warned that tournament venues are potential targets for terrorist attacks .
The drill included a bomb attack followed by armed gunmen at the city's fan zone where supporters will gather to watch matches live on a big screen.
Special forces secured the venue before emergency response teams treated the critically injured.