Lancashire Police Chief Stuart Williams said Wednesday police brought the victim to a local hospital to be checked out after they realized they had used the weapon against the wrong man.
He says police "deeply regret" the incident, which happened after police received multiple reports that a man was walking through the town of Chorley "armed with a samurai sword."
Williams says an urgent investigation has been launched into the incident and that the matter will also be reviewed by the Independent Police Complaints Commission.
Police say a different man was arrested in connection with the sword reports, but was not charged with any crimes.
(Copyright 2012 by The Associated Press. All Rights Reserved.)