POTSDAM, Germany (REUTERS) - A German man was jailed for life on Tuesday (July 26) for murdering a four-year-old refugee boy whom he had kidnapped from Berlin's main migrant registration centre and another child.

The man, identified only as Silvio S, confessed last year to abducting, sexually abusing and killing Mohamed Januzi, a Bosnian boy whose family was seeking asylum in Germany, prosecutors said.

He also admitted kidnapping a six-year-old boy called Elias near the child's home in Potsdam outside Berlin and murdering him in July 2015.

Silvio S, 33, remained silent for most of the trial but expressed his remorse to the relatives of his victims in a short statement towards the end of the trial.

"There are no words in the world that could describe how sorry I am. If I could make it undone, I would. I can't even forgive myself," German media reported him as saying.

The Bosnian boy disappeared on Oct 1 while waiting outside Berlin's central registration office for migrants with his mother and two siblings.

Silvio S was arrested at the end of October after his own mother told police he had told her he was involved.

The child's body was later found packed in cat litter in the boot of his car.

German prosecutors said the suspect had admitted to taking Mohamed to his flat and sexually abusing him.

He strangled the child the following morning when he wouldn't stop crying.

During questioning, Silvio S also confessed to the murder of Elias.