MOSCOW – Viktor Chernomyrdin, who founded the world's biggest gas company Gazprom and helped steer Russia through the chaos that followed the collapse of the Soviet Union, died Wednesday aged 72.

The longest serving prime minister in post-Soviet Russia, Chernomyrdin played a decisive role in supporting former President Boris Yeltsin during some of the darkest moments of the 1990s, negotiating with Chechen rebels and even holding the reins of power while Yeltsin underwent heart surgery in 1996.

The former mechanic will go down in history for his creation of Gazprom, which holds 17 percent of the world's natural gas reserves and is by far the Kremlin's most powerful economic card on the world stage.

President Dmitry Medvedev and Prime Minister Vladimir Putin expressed their condolences to Chernomyrdin's family and friends. The Kremlin said he died in the early hours but gave no cause of death.

As head of the Soviet Gas Ministry, Chernomyrdin foresaw the importance of the market as the Soviet Union crumbled. In 1989, he folded the Soviet Union's most lucrative gas assets into a new concern called Gazprom.