Police say a white gunman killed at least nine people at historic African-American church in city of Charleston.
An unknown gunman has killed at least nine people at a historic African-American church in the US city of Charleston, in what police called a hate crime.
Several people were reported to have also been injured in the shooting on Wednesday evening, and police said the suspect remained at large.
Charleston Mayor Joe Riley called the shooting "an unspeakable and heartbreaking tragedy".
The suspect was described as a 21-year-old white man wearing a sweatshirt, jeans and boots, Charleston police said in a message on Twitter.
"I do believe that this is a hate crime," Gregory Mullen, police chief of Charleston, told reporters.
Charleston Police Department spokesman Charles Francis said the shooting occurred at the Emanuel AME Church around 01:00 GMT. He had no information on victims.
The church pastor Clementa Pinckney, who is also a state senator, reportedly was among the dead. Officials did not immediately release the names or any details of the victims.
Earlier on Wednesday, Pinckney met with former US Secretary of State Hillary Clinton, who visited South Carolina as part of her presidential campaign.
A bomb threat was later reported near the scene of the church shooting, Charleston County Sheriff's Office spokesman Eric Watson said.
People who were gathered in the area were told by police to move back.
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.
A group of several men stood in a circle in front of a hotel near the church. "We pray for the families, they've got a long road ahead of them," Reverend James Johnson, a local civil rights activist, said during the impromptu prayer service.
The website for the church said it has one of the largest and oldest African-American congregations in the region. It was built in 1891 and is considered a historically significant building, according to the National Park Service.
Following the incident, US presidential candidate Jeb Bush cancelled his visit to Charleston later on Thursday.