Four Confederate battle flags were found on Thursday at the historic Atlanta church where civil rights icon Martin Luther King Jr. once preached, in a chilling reminder of the shooting of nine African-Americans at a South Carolina church in June.

The small flags, which a custodian discovered spread out on the ground outside the Ebenezer Baptist Church early Thursday morning, were intended to send a message of racial hate, church leaders said.

"This is the same as placing a swastika on the campus of a Jewish temple," said Rev. Raphael G. Warnock, Ebenezer's senior pastor, said at a press conference. "Whatever the message was, clearly it is not about heritage, but about hate."

The flag, carried by Confederate troops on the losing side in the US Civil War, is viewed by many as a symbol of the Southern legacy of slavery and racial segregation. But others hail it as an emblem of Southern heritage.

The incident follows the massacre at Charleston's Emanuel African Methodist Episcopal Church, a bedrock of black identity since the days of slavery.

Dylan Roof, the white man charged in the slayings, brandished the Confederate battle flag in online photos. In a manifesto posted on the site, he said he hoped the shooting would trigger a race war in the United States.

The massacre prompted the removal of the flag from the grounds of the South Carolina State House and soul-searching about race relations across the country.

In Atlanta, one of the flags was placed under a banner a that read "Black Lives Matter, Hands Up" an anthem taken up by protesters in the wake of a spate of police killings of unarmed black men.

The incident is being investigated by both Atlanta police and federal authorities, including Homeland Security and the National Park Service as the church and its campus are national landmarks.

The campus includes King's boyhood home and the church where King and his father, Martin Luther King Sr., were pastors.

Atlanta Police Chief George Turner would not rule out a connection with the Charleston shooting or say whether it was an act of terrorism.

Church security cameras caught the image of two males placing the flags overnight, Turner said.