IAMI, Aug. 20 — Three officials in Florida have received death threats as the state prepares for the nation's first execution of someone convicted of murdering a doctor who performed abortions, investigators said today.

The threats were made in letters sent on Monday to the Florida attorney general, the state corrections secretary and the warden at the Florida State Prison, where the convicted man, Paul Hill, is to be executed on Sept. 3 for fatally shooting a doctor and his volunteer escort at a Pensacola clinic in 1994.

The Florida Department of Law Enforcement did not disclose the wording of the threats and refused to comment on reports that the letters also contained bullets.

"We really can't say anything because it is an ongoing investigation," a department spokeswoman, Kristen Perezluha, said.

Dr. John Britton, 69, and his safety escort, James Barrett, 74, were shot and killed as they arrived in Dr. Barrett's pickup truck at the Ladies Center on July 29, 1994. Dr. Barrett's wife, June, who was also in the truck, was wounded.

Mr. Hill, a former minister and frequent protester against abortion, told the police who arrested him shortly after the shooting that "no innocent babies are going to be killed in that clinic today," according to trial records.

He acted as his own lawyer and did not call any defense witnesses. He had sought to argue that the killings were justified because they prevented abortions. The judge barred that defense because abortion is legal.

Death penalty opponents urged Gov. Jeb Bush to commute Mr. Hill's sentence to life imprisonment, with one group saying that making him a martyr could inspire more killings.

"Jeb Bush is giving Hill and his followers a platform to encourage others to copy the crime," said Abraham Bonowitz, director of Floridians for Alternatives to the Death Penalty.

Mr. Bush's office replied that the governor had thoroughly reviewed the case before signing the death warrant and "he determined there was no reason to alter the court-imposed sentence in Mr. Hill's case."