ATLANTA --- A death row inmate who has drawn international headlines with claims that he is innocent of killing a Savannah police officer is scheduled to be executed later this month, Georgia authorities said Wednesday.

Troy Davis, who is on death row for gunning down a Savannah police officer in 1989, is scheduled to die Sept. 23. Mr. Davis contends he should be granted a new trial after several witnesses who testified against him have recanted their statements.

The execution order was signed by Georgia Attorney General Thurbert Baker six months after the Georgia Supreme Court narrowly denied his request for a new trial.

An appeal has been filed to the U.S. Supreme Court, but the court is not scheduled to discuss the case until days after the impending execution.

The state's decision drew a sharp rebuke from Amnesty International, a human rights group that has worked to draw attention to the case.

"We're shocked and appalled that the attorney general short-circuited justice by setting an execution before letting the Supreme Court weigh in," said Jared Feuer, the group's southern regional director.

Mr. Davis was convicted of the 1989 murder of 27-year-old officer Mark MacPhail, who was working off-duty as a security guard at a bus station.

Witnesses identified Mr. Davis as the shooter. A jury convicted him in 1991 and sentenced him to death. At the trial, prosecutors said he wore a "smirk on his face" as he fired the gun, according to records.

But Mr. Davis' lawyers say new evidence could exonerate their client and prove that he was a victim of mistaken identity.

Several witnesses who initially testified against Mr. Davis have since recanted or contradicted their testimony. And three others who did not testify have said another man, Sylvester "Red" Coles -- who testified against Mr. Davis at the trial -- confessed to the killing.