Police respond to a shooting at the Emanuel AME Church in Charleston, South Carolina June 17, 2015. A gunman opened fire on Wednesday evening at the historic African-American church in downtown Charleston, South Carolina, a US police official said. [Photo/Agencies]

CHARLESTON, S.C. - A white gunman killed nine people at a historic African-American church in Charleston, South Carolina, the city's police chief said on Thursday, describing the attack as a "hate crime".

The suspect, who police described as a 21-year-old white man wearing a sweatshirt, jeans and boots, was still at large hours after the shooting on Wednesday evening.

Eight victims were found dead in the church, Chief Gregory Mullen told reporters at a media conference, and a ninth person died after being taken to a hospital. One other person was wounded and receiving treatment.

Mullen said: "It is unfathomable that somebody in today's society would walk into a church when people are having a prayer meeting and take their lives."

None of the victims were immediately identified. But the Reverend Al Sharpton, the New York-based civil rights leader, said in a Tweet that the Reverend Clementa Pinckney, the church's pastor and a member of the state Senate, was among the fatalities.

The shooting occurred at the Emanuel AME Church in the historic centre of downtown Charleston around 9 p.m. (0100 GMT), according to Charleston Police Department spokesman Charles Francis.

After the shooting, a bomb threat was reported near the church, Charleston County Sheriff's Office spokesman Eric Watson said, and people who were gathered in the area were told by police to move back.

Chief Mullen told the press conference that the all-clear had been given after checks following the bomb threat.

A police chaplain was present at the scene of the shooting, and a helicopter with a searchlight hovered overhead as officers combed through the area.