THE US judge presiding over the Charleston church shooting case has previously been reprimanded for using racist language.

County Magistrate James Gosnell Jr, who will hear the trial of 21-year-old Dylann Roof, was criticised for using the word "n*****" in a previous trial.

Roof is accused of killing nine members of a prominent black church in South Carolina in an attack which officials are treating as a hate crime.

As Roof appeared in court on Friday, Judge Gosnell said: "We have victims - nine of them. But we also have victims on the other side. There are victims on this young man's side of the family."

The judge was previously reprimanded in 2003 when he told a defendant: "There are four kinds of people in this world -- black people, white people, red necks, and n*****s."

The comments led to a disciplinary hearing in which Judge Gosnell was publicly reprimanded, but he was allowed to retain his position as Charleston's chief magistrate.

Six women and three men were shot and killed at the Emanuel African Methodist Episcopal Church on Wednesday night, including the church's pastor, Reverend Clementa Pinckney.

Following the atrocity, civil rights activists have questioned why it is not being treated as terrorism.

Nihad Awad, executive director of the Council on American-Islamic Relations, a civil rights advocacy group, said: "We have been conditioned to accept that if the violence is committed by a Muslim, then it is terrorism.

"If the same violence is committed by a white supremacist or apartheid sympathizer and is not a Muslim, we start to look for excuses: he might be insane, maybe he was pushed too hard."

Dean Obeidallah, a Muslim American radio show host and commentator, also claimed it should be obvious that the Charleston killer was a terrorist.

Many people also took to social media in the aftermath of the attack to hit out at the terminology used by Attorney General Loretta E. Lynch and South Carolina officials, who have described it as a hate crime.

The shooting has also sparked debate over the Confederate flag, which represents the region that seceded from the Union in 1861 in defence of slavery.

The flag, which continues to fly in the grounds of South Carolina's state capital building, has inflamed feelings in the wake of the tragedy, with many claiming it is insulting to the victims.

State legislator Norman Brannon has announced plans to introduce a Bill to remove the divisive symbol.