Media playback is unsupported on your device Media caption Lt Curtis Wilson: "The student was asked to leave the class several times, she refused and the officer acted"

A US sheriff's department says it is investigating after a video emerged showing an officer throwing a female pupil across a classroom.

The footage posted online on Monday was said to be filmed in a school in Columbia, South Carolina.

US media said the pupil had refused to leave the classroom when asked. The school "resource officer" was called.

The American Civil Liberties Union (ACLU) said there was "no justification" for the incident.

The officer is white and the female student, who was unharmed, is black, the sheriff's office said.

The incident comes at a time of increased scrutiny of police and their use of force against African Americans.

"It's very disturbing what happened today," said Richard County Sheriff Leon Lott, who has requested a federal investigation on the incident.

In a video obtained by South Carolina's WIS network, the officer, Ben Fields, is seen confronting the pupil, who is sitting at her desk. They then exchange words.

Mr Fields had been assigned to the school and was meant to protect students and faculty and promote anti-crime and anti-drug initiatives.

Image copyright Richland Country Sheriff's Department Image caption School resource officer Ben Fields

He then appears to restrain her around the neck, before quickly pulling her and her desk backwards to the floor.

The video shows him throwing the pupil a few metres across the classroom. She is then restrained.

Throughout the incident, other pupils remain seated, but some stand up and comment when the pupil is on the floor.

The video does not show what happened before the officer arrived.

What does a 'School Resource Officer' do?

places an officer in a school full-time as part of a "community policing" practice

offers programmes to reduce "crime, drug abuse, violence and provide a safe school environment"

accompanies school groups to athletic events and school trips

for younger children, they provide anti-drug programming

described as having schools as their "beat"

source: Richland County Sheriff's Department

The footage has been widely shared internationally on social media, with the term #AssaultatSpringValleyHigh used by many on Twitter.

The State newspaper in Columbia reported that the pupil and a male student were detained for breaching the peace.

Sheriff's spokesman Curtis Wilson told a press conference the girl had been asked to leave the classroom "several times" before the officer was called.

The officer has been taken off front-line policing while a sheriff's department investigation takes place, Mr Wilson said.

Debbie Hamm, the district's school superintendent, said in a statement that authorities were "deeply concerned" over the incident.

The state's ACLU said such "egregious use of force" against young people in class was "outrageous".

One group called the Richland Black Parents Association said the video "revealed what many African American parents have experienced in this district for a very long time."

Security in US schools