A Pakistani judge yesterday convicted a man of murdering 100 children and sentenced him to be strangled with an iron chain, chopped into pieces and dissolved in acid in front of the parents of his victims.

The grisly sentence for Pakistan's worst serial killing comes after a trial in which Javed Iqbal, 38, at first admitted the killings and produced a diary of his crimes before retracting his confession.

"Javed Iqbal has been found guilty of 100 murders. The sentence is that he should be strangled 100 times," Judge Allah Baksh told the court in Lahore. "His body should be cut into 100 pieces and put in acid, as he did with his victims."

The judge, apparently guided by Islamic Sharia law, ordered that the death penalty should be carried out in a large park in Lahore by the Minar-i-Pakistan, a national monument.

Pakistan's interior minister, Moinudeen Haider, criticised the sentence. "This will be challenged in the high court. Such punishments are not allowed," he said. Iqbal's lawyer said he would appeal.

Although Sharia law governs some aspects of Pakistani life, including a ban on alcohol and laws on blasphemy, there are no public punishments. The death penalty is carried out privately in prisons.

A 17-year-old boy was sentenced to death as an accomplice and two other men accused in the case were jailed for 14 years.

The horror of Iqbal's killings emerged in December when he wrote an anonymous letter to police claiming he had been killing runaway children and dissolving them in acid for months in his home in a slum near the Ravi Road in Lahore. "I have killed 100 beggar children and put their bodies in a container," he wrote.

Police found vats of acid in his house, human bones from two bodies and piles of children's clothes.

Despite a manhunt in which dozens of people were detained Iqbal eluded police for a month. He was arrested only after he walked into a newspaper office to give himself up. "I am Javed Iqbal, killer of 100 children," he told staff. "I hate this world, I am not ashamed of my action and I am ready to die. I have no regrets. I killed 100 children."

Iqbal said his killings were in revenge for brutal treatment received at the hands of the police after his arrest in the past.

He produced a 32-page diary detailing his sexual abuse and murder of the victims and including children's photographs.

Pictures and television footage of weeping parents poring over piles of children's clothes recovered from his home stunned Pakistani society, which began to question the depth of its concern for its vast, impoverished underclass. Some of the victims had been missing for more than six months before their parents reported their disappearance to police.

Last month Iqbal withdrew his confession and pleaded not guilty, saying he had invented his story to highlight the problems of runaway children. Before he was led away yesterday he repeated that he was innocent. No forensic evidence linked him to the crime and no more bodies were found.