The flyer, which is being handed out by police at the UK's busiest rail stations, shows worried commuters, running downstairs, hiding in dark corners and calling their relatives.
It insists: "If you hear gunfire or a weapons attack, leave the area safely if you can.
"If this puts you in greater danger, find a safe place to take cover."
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However the flyers have been slammed for 'spreading terror' and 'scaremongering' by social media users, who were left baffled when they received the leaflet.
Paul Crowther, chief constable of the British Transport Police (BTP), said passengers using public transport should be alert to the threat of terrorism.
He explained: "More than six million people travel on our railways every single day.
"For commuters, who make the same journey over and over again, it can be easy to become oblivious to their surroundings.
"But I would urge them to remain alert, use their instinct and have the confidence to report anything that strikes them as out-of-place or suspicious."
His comments come a few months after the terror threat level in the UK was raised from substantial to severe, meaning a terrorist attack is "highly likely".
Do you think these flyers are the best way to deal with the terror threat? Let us know via the comments box below.