New Delhi, In revelations that have shocked even his interrogators, serial killer and rapist has admitted to raping and murdering more than 30 children in and around Delhi, police said on Tuesday.

"Kumar has confessed to murdering more than 30 children after raping them," Deputy Commissioner of Police Vikramjit Singh said. "Most of the cases have taken place in and around Delhi."

Singh said that on Monday Kumar — who hails from Kasganj in Uttar Pradesh but has been living in Delhi — was taken to Narela, Bawana and Alipur, the places in outer Delhi identified by him during interrogation.

"This helped us to establish the fact (about the number raped and killed)," the officer said.

"I am myself monitoring the case. The investigations till now suggest that the toll might reach 40," he added.

Until now, police had thought the number of Kumar's victims would be around 15.

Police have mounted a massive operation to know if the cases of missing children filed in the past five years in Vijay Nagar, Bawana, Narela, Alipur, Begumpur, Kanjhawala, Samaypur Badli and other areas are related to this case, Singh said.

The 24-year-old Kumar began his crime spree sometime in 2008, the officer said.

Last year, Kumar was arrested for assaulting a minor boy in Begumpur in south Delhi. He abducted the boy near his house and fled after slitting his throat.

He assumed the boy was dead. But the victim survived as police found him bleeding in a septic tank of an under-construction building, the officer said.

Kumar was let off in that case — because at that time police did not know about the enormity of his saga.

He was again arrested on July 16 for raping and murdering a six-year-old girl in Begumpur. The girl had gone missing on July 14.

(IANS)