It also offers a motive for the heinous crime, one of the most shocking multiple murders of recent years, in a nation familiar with mass shootings.
"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," a text on the website reads.
US media became aware of the online manifesto only today, although it appears to have been in existence before the horrific massacre that has stunned the nation.
However, US media said the website was registered in February under Dylann Roof's name.
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A section of the manifesto, entitled "an explanation" reads: "I have no choice. I am not in the position to, alone, go into the ghetto and fight."
The text was referring to the right-wing extremist group Ku Klux Klan.
In the photographs, Roof is shown wearing a black jacket with flags from apartheid-era South Africa and Rhodesia (which includes the region now known as Zimbabwe), some of the most oppressive governments of modern times.
The website, entitled "The Last Rhodesian," can be found at lastrhodesian.Com.
Roof also is seen posing with wax reproductions of slaves in other photographs, holding a 19th century-era Confederate flag from southern states where slavery was practiced, standing at the site of a slave plantation and pointing a handgun at the camera.
Among the racist rants on the website, Hispanics are described as "our enemies," while "Negroes" are described as having a lower IQ and impulse control.