Russian energy company Gazprom announced it appointed Alexei Miller to serve for another five-year term that would end in 2021.

"The board of directors addressed the issue of electing Gazprom Management Committee Chairman and unanimously decided to re-elect Alexei Miller as Gazprom Management Committee Chairman for a 5-year term starting from May 31, 2016," the company said in a statement.

Miller served as the deputy energy minister in Russia before ascending to the chairman position at Gazprom in 2001. He was last re-elected to another five-year term in a unanimous board move in 2011.

Russia holds the largest reserves of natural gas in the world, accounting for about a quarter of the world total of proven reserves. The gas sector is controlled almost exclusively by state-run energy company Gazprom, which faces antitrust pressure from European economies given its control of both reserves and export arteries.

Lower energy prices are hurting exporting nations like Russia. In December, Russian Deputy Energy Minister Kirill Molodtsov warned gas production for full-year 2015 could come in at around 2 percent lower than the previous year.

Igor Artemyev, the head of Russia's Federal Antimonopoly Service, in October suggested a breakup of Gazprom in an effort to address leverage concerns.

Under Miller's tenure, Gazprom said total sales gas natural gas increased 9 percent compared with the same period in 2014. In terms of volume, gas deliveries to European and other regional countries were up 2 percent from the previous year.