A chilling video has emerged showing suspected Charleston church shooter Dylann Roof sitting quietly among the bible study group moments before he allegedly shot dead nine people.

The Snapchat video was posted by one of the victims, showing the members of the congregation sitting around a table before the attack, Mashable has reported.

Dylan Roof.

A man believed to be 21-year-old Roof can be seen sitting among them.

The wesbite said the video was posted by Tywanza Sanders, the youngest victim of the massacre, and had been confirmed by four friends.

Surveillance footage of the suspect wanted for the massacre. (Charleston Police Department) (Charleston Police Department)

Nine people inside the church were shot dead. (AFP)

The church is reportedly the oldest of its kind in the south. (AAP) (AAP)

The shooting at the Emanuel African Methodist Episcopal Church in the South Carolina city was one of the worst attacks on a place of worship in the country in recent years, and comes at a time of lingering racial tensions.

Roof was arrested during a traffic stop in Shelby in neighbouring North Carolina, about 370km north of where the massacre occurred.

He was allegedly carrying a firearm when stopped.

Churchgoers had gathered on Wednesday evening when the shooter walked into the building, sat in the congregation for about an hour and then opened fire, Chie Mullen said.

Three men and six women were killed, and several other people were wounded. Among the dead was the church's pastor Clementa Pinckney, who was also a South Carolina state senator.

A relative of one of the victims told MSNBC Roof had reloaded five times during the attack, according to a survivor.

Mourners react to the shootings. (AAP) (AAP)

"He said, ‘You rape our women and you’re taking over our country and you have to go'," Sylvia Johnson said.

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

A picture on Roof's Facebook page showed him wearing a black jacket with patches of the apartheid-era South African flag and the flag of white-ruled Rhodesia, which is now part of Zimbabwe.

It is believed Roof was given a .45 calibre handgun by his father for his birthday in early April.

The killings have racial overtones and come just two months after unrest broke out in the town of North Charleston, which borders on Charleston, over the killing of a fleeing unarmed black man by a while police officer.

“The only reason someone would walk into a church and shoot people that were praying is hate," said Joe Riley, the city's mayor.

Mullen called the killings a hate crime and said the FBI was involved in the investigation because of the "size and scope" of the crime

Senator Clementa Pinckney is believed to have been one of the victims. (Supplied) (Supplied)

The shooting occurred at a church in Charleston. (Twitter - @Bipartisanism) (Twitter)

South Carolina Governor Nikki Haley called the killings a "senseless tragedy".

"While we do not yet know all of the details, we do know that we'll never understand what motivates anyone to enter one of our places of worship and take the life of another," she said on Facebook.

Mayor Riley referred to the "unbelievable" slaughter of people praying at the "ritual" of a Wednesday evening prayer meeting.