Gunman sat down in church before opening fire, killing nine and letting one witness live

A 21-year-old white gunman accused of killing nine people at a historic African-American church in Charleston, South Carolina, was arrested on Thursday, said US officials, who are investigating the attack as a hate crime.

Law enforcement officials caught alleged gunman Dylann Roof, whose rampage on Wednesday came in a year that has seen months of racially charged protests across the United States over killings of blackmen.

US Attorney General Loretta Lynch told reporters that a suspect had been taken into custody hours after the shooting.

The gunman had killed nine people during a prayer service at the church, the city's police chief said on Thursday.

Charleston NAACP President Dot Scott told the Post and Courier newspaper that a survivor told family members the gunman first sat in the church before rising and opening fire. The shooter told her he would let her live so she could tell others what had happened, according to Scott.

Roof is from the area near Columbia, the South Carolina state capital, the Post and Courier reported. Columbia is about a two-hour drive from Charleston.

Officers with dogs searched the streets for the suspect after gunfire erupted inside Emanuel African Methodist Episcopal Church in downtown Charleston on Wednesday night, Police Chief Gregory Mullen said.

"The only reason that some-one could walk into a church and shoot people praying is out of hate," said Charleston Mayor Joseph Riley. "It is the most dastardly act that one could possibly imagine, and we will bring that person to justice. ... This is one hateful person."

The shooting recalled the 1963 bombing of a church in Birmingham, Alabama, that killed four black girls and galvanized the civil rights movement of the 1960s.

The Charleston church is one of the largest and oldest black congregations in the South, its website says. Its roots extend to the early 19th century, when it was founded in part by a freed slave who was later executed for organizing a revolt, according to the US-National Park Service.

The community reacted with shock and grief after Wednesday's shooting.

"I'm heartbroken," said Shona Holmes, 28, a bystander at the site in the aftermath. "It's just hurtful to think that someone would come in and shoot people in a church. If you're not safe in church, where are you safe?"

The FBI, the US Bureau of Alcohol, Tobacco, Firearms and Explosives and other agencies have joined in the investigation, Mullen said.

Eight victims died in the church, Mullen told reporters; a ninth died after being hospitalized. One other person was wounded and was being treated at a hospital, Mullen said, adding that there were other survivors. 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 dead.

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.

AFP - Reuters - AP