Police are searching a garden allotment in the northern German city of Hanover in connection with the disappearance of British girl Madeleine McCann, prosecutors said Tuesday.

"I can confirm that the search is being carried out in connection with our investigations into the Maddie McCann case," Brunswick prosecutor Julia Meyer told AFP, when asked about the move first reported by local newspaper Hannoversche Allgemeine Zeitung.

Police revealed in June that they were investigating a 43-year-old German man over the 2007 disappearance of three-year-old "Maddie", saying they believe he killed her.

Madeleine went missing from her family's holiday apartment in the Portuguese holiday resort of Praia da Luz on May 3, 2007, a few days before her fourth birthday, as her parents dined with friends at a nearby tapas bar. 

Despite a huge international manhunt, no trace of her has been found, nor has anyone been charged over her disappearance.

The suspect, who was not named by police but identified by German media as Christian B., has a history of previous sex offences including child sex offences and rape. He is currently serving a sentence for drug trafficking in Kiel.

He has applied to be released early on probation after having completed two-thirds of the sentence, with a decision still pending. 

A court in Brunswick had separately sentenced Christian B. to seven years in prison last December for an assault against a 72-year-old American tourist in 2005 - in the same seaside village of Praia da Luz where Maddie went missing.

But that sentence has not yet been finalised pending an appeal by the defendant's lawyers over extradition technicalities.

According to police, the suspect lived in the Algarve region of Portugal between 1995 and 2007. 

He made a living doing odd jobs in the area where Madeleine was taken, and also burgled hotel rooms and holiday flats.