(CNN) -- Saudi Arabian officials beheaded and then publicly displayed the body of a convicted killer in Riyadh on Friday, an act that prompted a stiff denunciation by a leading human rights monitor.

The Saudi Interior Ministry said Ahmed Al-Shamlani Al-Anzi was sentenced to death and then "crucifixion" -- having his body displayed in public -- for the kidnapping and killing of an 11-year-old boy and for the killing of the boy's father, according to the official Saudi Press Agency.

Amnesty International issued a statement deploring the punishment, with the group's Hassiba Hadj Sahraoui saying in a statement it is "horrific" that beheadings and crucifixions "still happen."

Even though the word "crucifixion" is used to describe the public display, the act has no connection to Christianity and the crucifixion of Jesus. The bodies are not displayed on crosses, Lamri Chirouf, who researches Saudi Arabian issues for Amnesty, explained.

The Saudi Interior Ministry asserted that Al-Anzi's body was displayed as a warning that those involved in similar crimes would suffer the same fate, the press agency reported.

The ministry said Al-Anzi kidnapped the boy and held him for a "malicious purpose" at a grocery store where he worked. He tied rope around the boy's neck and strangled him to death, the ministry said.

When the boy's father came to the store looking for his son, Al-Anzi axed the father repeatedly until the man died. When police came to arrest Al-Anzi, Al-Anzi resisted arrest by threatening them with a knife.

Police later discovered that Al-Anzi had been previously convicted of other crimes, including possession of pornographic videos and sodomy, the Interior Ministry said.

Chirouf, the Saudi Arabian researcher for Amnesty International, said his understanding of how the Saudi government carries out crucifixion jibed with Saudi Press Agency's account.

Government officials do use crucifixions, or public displays of executed bodies, as a tool to deter people from committing such a crime, he said.

This latest case was classified as an offense of rebellion, one that basically rejected all of the rules of religion and society, he said.

Chirouf said those crucified are beheaded first and then their heads are sewn back on their bodies. Then, the corpse is mounted on a pole or a tree.

The English-language Saudi Gazette newspaper said the body was placed on public display throughout the evening and Chirouf said it was his understanding that the body was to be displayed for a few hours.

In its denunciation of the punishment, Amnesty International deplored the "extensive use of the death penalty" in Saudi Arabia.

"King Abdullah should show true leadership and commute all death sentences if Saudi Arabia is to have any role to play as a global leader or member of the G-20," Sahraoui said.

The group asserts that "trial proceedings" in the country "fall far below international fair-trial standards."

"They usually take place behind closed doors without adequate legal representation. Convictions are often made on the basis of "confessions" obtained under duress, including torture or other ill-treatment during incommunicado detention," Amnesty International said.

"Those who are sentenced to death are often not informed of the progress of legal proceedings against them or of the date of execution until the morning when they are taken out and beheaded."

Amnesty International said there were 102 executions in Saudi Arabia in 2008 and is aware of 136 people believed to be awaiting execution. It says there has been "a high number of executions of migrant workers and other foreign nationals, in particular from Asia and Africa."

Al-Anzi was a Saudi national, said Chirouf -- who added "nobody knows how many people are on death row" in Saudi Arabia.

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