So they lured their 16-year-old friend Clara Garcia to a patch of wasteland, persuaded her to close her eyes for a "surprise" and stabbed her 18 times with a kitchen knife. Then they went out drinking with friends.

Spaniards have looked on aghast at the trial of the girls, who are aged 16 and 17. Yesterday they were sentenced to eight years of youth custody.

Neither has shown remorse for the murder, in May last year. They had sought, and found, the thrills of murder and the fame that came with it, they told police.

Clara, a friend who previously shared their taste for black, gothic clothing and the horror stories of Dean Koontz, had simply been the easiest victim they could think of.

She had been spending less time with them since finding a boyfriend and they claimed she had become "weak" and "normal".

Clara, whose body was found in the morning by her boyfriend, had bled to death. Police, who knew she had arranged to meet her friends, found the knife and blood-stained clothing at the homes of the two girls, whose full names cannot be revealed because they were minors at the time of the crime.

Crowds of angry neighbours gathered around the court house door to hurl insults at the two girls as they were driven off. "They acted with caution, premeditation and in full consciousness," the sentence issued by the juvenile court in Cadiz declared.

The savage killing of Clara Garcia has caused consternation in Spain. Psychologists and politicians fear that the increase in the number of children who apparently kill for kicks is a sign that the strong moral bonds of Spain's traditionally tight-knit families and close communities are beginning togive way.

"I think we are, in some way, all to blame," Clara's father, Jose Antonio Garcia, said.

Figures show that the number of murders, many of them similarly brutal and motiveless, carried out by under-18s has increased by 60% in the past six years. The killers had collected press clippings about recent murders in Spain, especially those committed by young people.

They had also written a fan letter to a 16-year-old from Murcia, south-east Spain, who last year used a samurai sword to hack to death his parents and his 11-year-old sister, who had Down's syndrome.

The youth, who will appear in court soon, has admitted his crime but has also shown no remorse for what police said was a brutal and carefully-planned, night-time attack.