TOKYO (AP) — Japan executed three murderers Tuesday, including a serial killer who mutilated the bodies young girls in the late 1980s in a case that triggered calls for tighter restrictions on violent pornographic videos.

Tsutomu Miyazaki, 45, who killed and mutilated four young girls, was hanged at a detention center in Tokyo, said Justice Minister Kunio Hatoyama.

Miyazaki burned the body of one 4-year-old and left her bones on her parents' doorstep. He also wrote letters to the media and victims' families taunting police. Japanese newspaper reports said he ate part of the hand of one of his victims and drank her blood.

The two others executed Tuesday were Shinji Mutsuda, 45, who had been on death row for the murder and robbery of two people, and Yoshio Yamasaki, 73, who was convicted of killing two people for the insurance money, the Justice Ministry said in a statement.

"I ordered their executions because the cases were of indescribable cruelty," Hatoyama said. "We are pursuing executions in order to achieve justice and firmly protect the rule of law."

Japan, one of the few industrialized countries that has capital punishment, has picked up the pace of executions over the past year amid rising concerns about violent crime.

The three executed Tuesday brought to 13 the number of death-row inmates hanged in the past six months under Hatoyama, an outspoken supporter of the death penalty. Only one inmate was executed in 2005.

In 1997, Tokyo District Court found Miyazaki guilty of killing four girls ages 4 to 7 years old in 1988 and 1989, and sentenced him to death. The Tokyo High Court upheld the sentence in 2001, and the Supreme Court followed suit on Jan. 17 this year, exhausting Miyazaki's appeals.

Miyazaki was also convicted of the abduction and sexual assault of a fifth girl.

The murders and Miyazaki's arrest dominated Japanese headlines, along with the discovery that his home was filled with a collection of thousands of violent pornographic videos, animated films and comic books stacked floor-to-ceiling.

The case triggered concerns that many young people had become desensitized to human suffering through the repeated viewing of graphic images in videos and comics.

Mutsuda was also hanged at the Tokyo detention center for killing two men and robbing them of $278,000 in 1995 and 1996. Yamasaki was executed in Osaka for murders committed in 1985 and 1990.

Hatoyama, who took office last August, denied his ministry was purposely picking up the pace of hangings. Three men were executed in December, three more in February and another four in April.