Police say a suspicious device that shut down a busy Frankston street was a fake bomb and have released CCTV footage of the man who left it there and fled the scene.

Fletcher Road was shut down for several hours on Tuesday morning as a bomb squad investigated "suspicious devices" left outside the Frankston Magistrates Court.

On Tuesday afternoon Victoria Police released footage which showed a man walking purposefully towards the courthouse at around 7am with his head down and a hoodie pulled tightly around his face.

The man is carrying what appears to be a brown paper bag, which he dumps in front of the building before running away.