WASHINGTON • The gunman accused of killing nine people at a South Carolina church last month plotted his attack for months, choosing his target because it was a nationally known, historically black church, US Attorney-General Loretta Lynch said in announcing federal hate crime charges against him.

Dylann Roof, 21, is also accused of killing people while obstructing religious freedom, a charge that carries a possible death sentence, though Ms Lynch said the Justice Department had not decided whether to seek it.

"He was looking for the type of church and the type of parishioners whose death would in fact draw great notoriety for his racist views," she said on Wednesday.

The authorities have linked Roof to a racist Internet manifesto and said he was in contact with white supremacist groups before his attack on the Emanuel AME Church, which has hosted many major civil rights leaders, including Martin Luther King Jr.

Roof already faces nine counts of murder in the state court and could face the death penalty there. But Justice Department and FBI officials say the Charleston shooting was so horrific and racially motivated that the federal government must address it.

South Carolina does not have a hate crime law and federal officials believe a murder case alone would leave the racial component of the crime unaddressed.

"The parishioners had Bibles," Ms Lynch said. "Dylann Roof has his .45-calibre Glock pistol and eight magazines loaded with hollow-point bullets."

Ms Lynch said Roof hoped the attack would "fan racial flames" and exact revenge for what he believed were wrongs that African- Americans committed against white people.

Before the shooting, he was photographed holding a Confederate battle flag and a handgun.

Survivors said Roof arrived at the church as worshippers gathered for a Bible study group and sat with them for a while before he started shooting.

"You are raping our women and taking over our country," Roof told the victims, all of them black, before killing them, witnesses said. While the shooting did bring new national attention to racial tensions, it did not have the effect that prosecutors say Roof wanted. Quite the opposite. The shooting renewed the debate in the US over the symbolism of the Confederate flag. South Carolina lawmakers responded by removing it from the State House grounds.

There are mixed views inside the Justice Department about whether prosecutors should try to bring the federal case, before Roof stands trial in South Carolina. Some said they believed it would be better to defer to local prosecutors, both because they have already started a case that they see as very strong, and because it avoids the lengthy federal process required when seeking the death penalty.

But many others say the shooting is precisely the kind of crime that Congress intended the federal government to prosecute when it enacted hate crime laws.

NEW YORK TIMES, REUTERS