Kazakh President Nursultan Nazarbayev is in hospital in Germany, but it is unclear what he is being treated for, the Bild daily reported on Tuesday. The 71-year-old \"secretly\" checked himself into the University Medical Center Hamburg-Eppendorf in northern Germany, and is being guarded by a heavy security detail, the paper said, without saying where it got the information. Contacted by AFP, hospital spokeswoman Christian Kreher declined to comment, saying she could neither confirm nor deny that Nazarbayev was there. She added however that the clinic had undertaken \"no special security measures.\" A Kazakh foreign ministry spokesman told AFP: \"The president is currently on holiday\" but without saying where. A statement dated July 11 on the presidential website akorda.kz said the holiday was \"brief\" but also gave no details. No further news has been published on the website since, except a statement of condolence on July 12 for the Volga cruise ship tragedy in Russia. Nazarbayev\'s chief advisor Yermukhamet Yertysbayev, contacted by AFP, declined to comment. The Bild report also said that the German foreign ministry had acted as a mediator in having the energy-rich Central Asian republic\'s president admitted to the clinic. Contacted by AFP, however, the ministry denied this and said it was unaware of Nazarbayev being in Hamburg. Nazarbayev came under strong criticism from international observers in April after he won re-election with a reported 95 percent of the vote.