The St. Petersburg International Economic Forum starts June 8 in Russia's second largest city, gathering hundreds of CEOs from top international companies. Gazprom is the main sponsor of the $19.4-million forum.
"During a planned medical check-up at a hospital, [Alexei] Miller was diagnosed with some health problems, requiring medical treatment for some time," Sergei Kupriyanov said.
He said the deputy chairman of Gazprom's management board, Andrei Kruglov, will head the company in the meantime, adding that the temporary absence of the CEO would not affect the company's performance.
According to some reports, Miller has previously complained about kidney problems.
About 10,000 people are expected to participate in the work of the economic forum and agreements worth $3.3 billion will be signed in the presence of Russian President Vladimir Putin and top Kremlin officials.
