FRANKFURT AM MAIN, GERMANY (AFP) - The case of a missing 15-year-old boy found in a closet at the flat of a suspected paedophile has gripped Germany, but his mother says she just wants to celebrate Christmas with her son.

Marvin had been missing for over two years when he was found hiding in a cupboard last Friday (Dec 20) as police searched the home of a 44-year-old man suspected of distributing child pornography.

The stunning discovery in the western town of Recklinghausen has drawn comparisons to two shocking cases in Austria - of Natascha Kampusch, who was held by her kidnapper for eight years before she managed to escape in 2006; and of Elisabeth Fritzl, who was kept in a cellar and repeatedly raped by her father Josef in an ordeal that lasted 24 years.

Marvin, who disappeared after saying goodbye to his carers at a youth shelter early on June 11, 2017, is currently in psychiatric care.

"I want to visit him for Christmas, to celebrate a little with him," his mother Manuela B., 53, told Germany's best-selling tabloid Bild.

A police spokesman on Monday said the decision on when Marvin can go home "is up to the doctors, not the police".

Many questions remain answered in the case that German media have dubbed an "Advent miracle" - including how the boy ended up at the flat and if he could have left at any time.

TV APPEAL

Police said in a statement that the officers who discovered him "did not see any indications at that point that he was being held against his will".

But Marvin's mother, who was briefly reunited with her son on Friday, doubted he was there entirely out of free will.

"The man whose place they found him at must have manipulated him," she told Bild.

"I could go crazy thinking about what's been done to him."

She said Marvin was found wearing the same clothes as on the day he vanished, and said he looked like "a broken old man".

"He now needs to process what's happened over the past two-and-a-half years. This is all so painful."

His stepfather Michael B. told the RTL broadcaster he believed the boy hadn't stayed at the flat voluntarily, adding that Marvin "didn't talk much" when he saw his mother.

Marvin was 13 when he was living in a care home for young people, reportedly after he had trouble processing the death of his father.

After the investigation into his disappearance had gone cold, Marvin's mother and sister made a fresh appeal for information in the TV show Aktenzeichen XY in July, which tries to solve missing cases.

But in the end, the boy's discovery appeared to be entirely coincidental.

Marvin's mother told Bild she already knows what she will give her son for Christmas.

"I want to give him new clothes."

The suspect at whose flat Marvin was found remains in custody and faces allegations of serious sexual offences.