Rush hour motorists were stunned when the officers swooped on a vehicle on the busy Earlsgate Roundabout in Grangemouth at tea time and detained a man.
No details of why he was detained have been released but it is understood it was not linked to terrorism.
A Police Scotland spokeswoman said: “Police Scotland armed officers, supporting a planned operation, detained a man from a vehicle at the Earlsgate Roundabout, Grangemouth.
“The operation was conducted around 6.15pm on Tuesday, May 30.
“This was part of an ongoing investigation. At no time were the public at any risk. We would like to thank any drivers who may have been delayed whilst officers dealt with this incident.”