A South Carolina school officer seen on video dragging a "disruptive" female student across a classroom has been sacked.

Richland County Sheriff Leon Lott said senior deputy Ben Fields "did not follow proper procedure".

"When he threw her across the room, he lost control of her and that is against our policy," he told a news conference on Wednesday.

"The manoeuvre he used was not based on training, nor was it acceptable."

However, the sheriff said the student was "responsible for initiating this action".

He told reporters that Mr Field was called into the classroom at Spring Valley High School after the "disruptive" 14-year-old refused to leave despite being told to do so by her teacher and a school administrator.

That was when Mr Fields was called into the classroom to remove her. She again refused, and the deputy told her she was under arrest, the sheriff said.

Video captured by other students on their mobile phones showed Mr Fields grabbing the student round the neck and flipping her backward on to the floor.

The 34-year-old deputy then dragged her out of the chair and across the floor.

The footage sparked an uproar over the actions of the officer, who is white, against the student, who is black.

The NAACP put out a statement saying race played a role in the arrest and that the officer should be charged, and the FBI is conducting a civil rights investigation at Sheriff Lott's request.

But the sheriff on Wednesday said both the teacher and the school administrator, who is black, supported Mr Fields' actions.

"Deputy Fields did wrong, and we take responsibility for that," he said before later adding, "we have to have discipline in our schools."

The student, who Sheriff Lott said hit the officer during the altercation, faces a charge of disturbing schools.

Her lawyer told ABC's Good Morning America that she suffered neck and back injuries and now has a cast on her arm.

Sheriff Lott had said on Tuesday that the girl was uninjured in the confrontation but "may have had a rug burn".