Modern history's worst murderer - a serial killer of hundreds of children - is about to be freed from prison after serving only 12 years.

Pedro Alonzo Lopez became known as the "Monster of the Andes" in 1980 when he led police to the graves of 53 of his victims in Ecuador - all girls between 9 and 12 years old.He was found guilty of murdering 110 girls in Ecuador alone and confessed to a police undercover detective to a further 240 murders of missing girls in neighboring Peru and Colombia. He has served slightly more than 12 years of a 16-year maximum sentence.

Now, Lopez, 41, said from his cell: "I will soon be a free man again. They are releasing me on good behavior."

Quizzed about Lopez's impending release, Prisons Minister Pablo Faguero admitted, "Yes, it does sound strange, but that is our law." Sixteen years is the maximum anyone convicted of murder can serve in Ecuador.

Just as other men shave, shower and eat, Lopez killed on a regular basis - slaying two, sometimes three girls every week, every month, over a three-year rampage.

Locked within his cell, watched by nervous guards holding cocked pistols, the serial killer, in his only interview ever, told me: "I am the man of the century. No one will ever forget me."

He tried to explain his killings, comparing himself to spectators who attend bullfights to watch the "moment of truth" - when the fighting bull or matador faces death. "The moment of death is enthralling and exciting. Only those who actually kill know what I mean," said the Monster of the Andes.

Lopez killed his young victims by luring them away from marketplaces with the promise of giving them trinkets such as hand mirrors.

"I walked among the markets searching for a girl with a certain look on her face - a look of innocence and beauty," he said.

"She would be a good girl, always working with her mother. I followed them - sometimes for two or three days - waiting for the moment when she was left alone."

He took them to secret hideaways where he had prepared graves. Sometimes there were bodies of earlier victims lying in the shallow pits.

Lopez lulled the innocents by cuddling them before raping and killing them - always at sunrise.

The killer also said he often followed, wanting to trap, the blond-haired children of visiting tourists. "But I never got the chance. Their parents were too watchful."

Lopez's crimes came to light in 1979 when a river overflowed near the town of Ambato, Ecuador, and the bodies of four girls were washed up on the banks. They had all been strangled.

Three days later, Lopez was captured as he tried to snatch 10-year-old Maria Poveda. Luckily for her, her mother, Carlina Ramon Poveda, saw Lopez walking away hand in hand with her daughter and screamed.

An angry mob pounced on the stranger, holding him until police arrived.

To find out whether Lopez had murdered the riverbank children, police placed undercover detective Pastor Gonzales in his cell.

Eventually Lopez revealed his whole terrifying story.

Gonzales said, "For 27 days I hardly slept, afraid I'd be strangled in my sleep. But I tricked Lopez into confessing by pretending I was a rapist, too. He boasted to me of murder after murder in Ecuador, Colombia and Peru.

"It was beyond my wildest nightmares. He told me everything."

Lopez took police to the graves of 53 of his victims, then refused to help further.

Two months later, in 1980, he pleaded guilty to 110 counts of murder.

Police said Lopez could have been charged with 350 murders of missing girls but additional trials in Colombia and Peru would have been too complex and costly.

Had he been extradited to Colombia, Lopez would have faced a firing squad upon conviction. But it never happened.

Lopez was already a convicted murderer before he started preying on girls.

He slit the throats of three men who had raped him as an 18-year-old in a Colombian jail where he was serving time for car theft.

Lopez said he knew from the age of 8 that he was going to be a killer: "I was the seventh son of 13 children of a prostitute in Tolima, Colombia.

"My mother threw me out when I was 8, and I was taken in by a man who raped me over and over again.

"I decided then to do the same to as many young girls as possible."

Victor Lascano, governor of the Ambato jail, where Lopez was first held, is terrified that he may strike again.

"God save the children. He is unreformed and totally remorseless. This whole nightmare may start again."

Police feel a lot of fathers and brothers of the murdered girls will be coming to Ecuador when the Monster of the Andes is released from Penal Garcia de Moreno.

"He won't live long," predicts Carlina Poveda, the mother of the young girl who helped in his capture.

"It will be a kindness to the world for someone to murder this fiend. The Monster of the Andes won't last long on the outside."