Outside the church, the oldest African-American congregation in the southern United States, bouquets, teddy bears and balloons covered the sidewalk while hundreds of people lined up to mourn, sing hymns and leave memorials.

Thousands of hand-written messages covered white banners at the church's entrance, reading "God Bless," or "Thank you Sen. Rev. Clementa Pinckney. You will 4ever be an inspiration," referring to the church's pastor, a state senator who was one of the victims.

City officials, religious leaders and mourners have said Sunday's services at Emanuel church would mark a small step toward healing after the latest U.S. mass shooting, which has again trained a spotlight on the nation's pervasive and divisive issues of race relations and gun crime.

Dylann Roof, the 21-year-old suspect, remains in jail charged with nine counts of murder. Authorities say he spent an hour in an evening Bible study group at the church, nicknamed "Mother Emanuel" for its key role in African-American history, before opening fire on Wednesday night.

Federal investigators were examining photos and white supremacist writings that surfaced on a website on Saturday that appeared to show Roof posing with a handgun and standing in front of a Confederate military museum and plantation slave houses.

Texts posted on the website included an "explanation" by the author for taking some unspecified action.

"I have no choice ... I chose Charleston because it is most historic city in my state, and at one time had the highest ratio of blacks to Whites in the country," it said.

The massacre was the latest in a series of mass shootings in the United States that have reignited a debate over gun control in a country where the right to own firearms is constitutionally protected.  

Outside Emanuel church on Sunday, where services were due to begin at 9:30 a.m. (1330 GMT), security was tight as police patrolled with a bomb dog to sniff through the growing piles of flowers, balloons, toys and signs.

Below the church program board, a poster covered in pink and white hearts and silver stars read: "We are all in this together & we will shine on." A picture of multi-colored hands marked the middle of the card, reinforcing the message.

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