German newspaper Bild reported this week that Nazarbayev, 71, had undergone a prostate operation in a Hamburg hospital and was recovering well. There has been no official confirmation of this from either Kazakh or German officials.

Nazarbayev, a member of the last Soviet Communist Party politburo, is the only leader independent Kazakhstan has known. He has ruled the oil-rich country since 1989, two years before independence, and won a landslide election victory in April.

The absence of a clear successor is viewed by most investors as the single biggest threat to political stability in Kazakhstan, Central Asia’s largest economy and the recipient of more than $120 billion in foreign investment since independence.

The presidential website, www.akorda.kz, said on July 11 that Nazarbayev was on a short holiday. On Thursday, it reported he had spoken to Uzbek President Islam Karimov to offer support and condolences after a major earthquake.

The website gave no details of Nazarbayev’s whereabouts.

But a spokesman for Prime Minister Karim Masimov, who declined to be identified, said: “A meeting between the prime minister and the president took place in Astana.”

Kazakh Foreign Minister Yerzhan Kazykhanov, speaking at a news conference in Berlin on Wednesday, said he expected the president to be back in his office on Thursday. He did not comment on the Bild reports.