A school security officer and a county sheriff's office in the United States have been sued for putting two Kentucky elementary school children in handcuffs.

The boy (8) and girl (9), both of whom have been diagnosed with attention deficit hyperactivity disorder (ADHD), had the handcuffs put around their biceps, with their arms locked behind them.

Distressing video footage shows the little boy crying and struggling as he sits on a chair.

In the video, which was captured by a school administrator, school resource officer Kevin Sumner tells the boy: "You don't get to swing at me like that. You can do what we've asked you to, or you can suffer the consequences."

The federal lawsuit claims the boy - who is 3ft 6ins tall and weighs 52lbs - was removed from class because he was not following the teacher's directions.

The boy then tried to leave the principal's office, but was physically restrained by school administrators until Mr Sumner arrived to escort him to the bathroom.

On the way back from the bathroom, he tried to hit Mr Sumner with his elbow, according to a report from the Kenton County Sheriff's office, and was then handcuffed.

The girl, who weighed 56lbs, was sent to an isolation room at her school last August for being disruptive.

School officials asked Mr Sumner to help after the girl tried to leave the room and was restrained by the principal and vice principal.

A report from the sheriff's office said Mr Sumner put the girl in handcuffs because she was "attempting to injure school staff".

The lawsuit claims the girl suffered "a severe mental health crisis" and Mr Sumner called for a "medical crisis team". She was taken to a hospital by ambulance for a psychiatric assessment and treatment.

Kentucky state regulations ban schools from physically restraining students that are known to have conditions like ADHD.

The lawsuit states that officials at both schools were aware of the students' ADHD, which is characterised by "impulsivity, difficulty paying attention, complying with directives, controlling emotions and remaining seated".

Susan Mizner, disability counsel for the American Civil Liberties Union which released the video, said: "Shackling children is not okay. It is traumatising, and in this case it is also illegal."

Robert Sanders, a lawyer for Mr Sumner, said he put the children in handcuffs because "they were placing themselves and other people in danger of harm and that's what the book says to do".

The American Civil Liberties Union (ACLU) has relased the video footage, which some may find disturbing: