TALLAHASSEE - Three death-threat letters containing bullets were sent to Florida's attorney general and two prison officials in protest of the pending execution of anti-abortion activist Paul Hill.

The missives arrived Monday as death-penalty opponents urged Gov. Jeb Bush to cancel the lethal injection execution scheduled for Sept. 3. They warn that Hill's death has the potential of turning him into a martyr to extreme anti-abortion groups.

State law enforcement officials said Tuesday they're investigating the letters and bullets, delivered in Tallahassee to Attorney General Charlie Crist and Corrections Secretary James Crosby. Joseph Thompson, the warden at Florida State Prison in Starke, also received a threat. Hill has been on Death Row there since 1994 for the shooting death of a Pensacola abortion doctor and his escort.

Investigators refused to release details about the letters, but said they were threatening in nature.

''We take these seriously,'' said Al Dennis, a spokesman for the Florida Department of Law Enforcement. ``The content of the letters were sufficient enough for us to open a criminal investigation.''

Dennis would not say whether security would be enhanced for the three men. The FDLE provides bodyguards for Bush and his family, and Lt. Gov. Toni Jennings is guarded by agents with the Florida Highway Patrol. Neither received such threats.

''I can assure you we're taking all the necessary steps and precautionary measures,'' Dennis said.

Florida Department of Corrections officials referred all questions to the FDLE. Crist, who is the state's chief legal officer, declined to discuss the threats, but said he's ''calm and confident'' that investigators will resolve the matter.

State officials asked the FDLE Tuesday to look into a website that antideath penalty activists had warned the governor about, saying it showed that some anti-abortion activists were viewing Hill's execution as martyrdom. The Christian Gallery website includes a link to ordering copies of the ''Paul Hill Issue'' of The Abortion Abolitionist, a newsletter that celebrates Hill as a hero.

In the lead story of the newsletter, publisher Neal Horsley titles his piece, ``Let Them Be Shown Bullets. Will Paul Hill's Death Unleash A Torrent of Death on America's Leaders?''

Below the headline is a photograph of Bush on the campaign trail, noting the governor signed Hill's death warrant. Bush has said he sees no reason to call off the execution.

Horsley says in the newsletter that most of his readers are ''confused, sad and grieving deeply,'' because they consider Hill ``a hero, an authentic Christian martyr, whose death proves the government of the United States of America has been enslaved by the forces of Satan.''

Some, Horsley said in the newsletter, have made 'thinly veiled direct threats of assassination and future death to the Governor of Florida and -- if the people who wrote the flyers quoted in this article are correct about `everyone associated with his death being at risk' -- even the brother of the Governor of Florida 'will be liable to eventually having their lives taken from them as a consequence.' ''

`A HARBINGER'

''Such evidence,'' Horsley concluded, ``leads great credibility to the idea that Paul Hill's death will be a harbinger of more death to come.''

Mainstream anti-abortion advocates have long distanced themselves from Hill and suggested his supporters are a fringe element.

''Any type of violence such as this is wrong,'' said Mike McCarron, executive director of the Tallahassee-based bishops' group, the Florida Catholic Conference. ``Thou shalt not kill -- that commandment cannot be suspended in instances that some feel it could be suspended and justified; the ends do not justify the means.''

Horsley, who lives outside Atlanta, told The Herald he functions as a news reporter and editor and said his newsletter seeks to explain the angst that Hill's upcoming execution is causing anti-abortion activists.

''All I know is I printed the news,'' Horsley said. ``I publish the facts in the same way that you are. I don't know a whit of difference between what I did and what you are doing but it gets spun that because I am opposed to legalized abortion that I am somehow willing to see people killed.''

He wouldn't say whether law enforcement officials had contacted him.

MAILED FRIDAY

The newsletter was mailed out Friday, Horsley said, to about 2,500 subscribers who pay $48 a year. Horsley also distributed copies Saturday to the media at a rally in Montgomery, Ala., in support of Alabama Chief Justice Roy Moore, who has been ordered by the federal government to remove a monument to the Ten Commandments from the state judicial building.

The Rev. Michael Bray, a Maryland anti-abortion activist and contributing editor to Horsley's newsletter, called Hill ''God's prophet'' in the newsletter and warns ``there will be consequences for the murder of God's messenger.''

Reached by phone to elaborate on the consequences, Bray demurred.

''Ill leave that to God,'' Bray said. ''I speak what I think is right and I let the chips fall where they may,'' Bray said. ``That type of action [killing a public official] doesnt depend on what I say. This is a statement of what is said in Scripture.''

Bray said he doesn't know who sent the threats to the Florida officials. But, he added, politicians and bureaucrats, just like everyone else, will reap what they sow.

''Each official doesnt stand only before the people. He stands before God,'' Bray said. ``By election, by crook, maybe as usurpers, theyre sitting in office because of God. And they will stand in judgment before him for their actions.''

Herald staff writers Marc Caputo and Joni James contributed to this report.