BERLIN (AFP) - The German suspected of kidnapping and killing a four-year-old Bosnian refugee has admitted to murdering another child, police said on Friday (Oct 30).

Following the confession, a body was found in a garden allotment, police said.

"The man confessed overnight that he had also killed Elias," said Berlin police spokesman Stefan Redlich, referring to a six-year-old German boy who has been missing since July.

Both children were victims of sex crimes, German news agency DPA said without citing its sources.

Police are also examining if the suspect, identified as Silvio S., had anything to do with a missing five-year-old girl called Inga, according to media reports.

The man was arrested Thursday after his mother told police that he may have been involved in the kidnapping of the Bosnian boy, Mohamed.

Police found the body of a child in the suspect's car which was packed in cat litter that appeared to have been dead for some time.

Prosecutors had on Thursday said the body, which was undergoing an autopsy, was likely to be that of Mohamed.

The boy had been missing since Oct 1, when his mother took him and his sisters to Berlin's main refugee registration centre known as Lageso which receives hundreds of asylum seekers daily.

The family has been living in Germany for more than a year and the mother had gone to the registration centre that day to obtain her social allowances, according to local media.

Police subsequently issued CCTV footage of a bearded man leading a child away who was holding a stuffed toy.