Yukos, once Russia's largest oil company, was declared bankrupt on August 1, 2006, after three years of litigation with tax authorities over arrears. Its founder, Mikhail Khodorkovsky, is serving an eight-year prison sentence in Siberia for fraud and tax evasion.
Khodorkovsky, who acquired oil assets through controversial privatization deals in the early 1990s, has insisted that his prosecution was orchestrated by the authorities to silence his criticism of President Vladimir Putin, and as part of a campaign to bring oil and gas assets under the Kremlin's control.
Through a series of liquidation auctions, Yukos has repaid the majority of its debt to creditors. The company's key production and refining assets have been bought up by Rosneft at, or following, auctions, making the state-controlled company one of the country's leading crude producers.
Creditors' claims to Yukos stood at 709 billion rubles (about $28 billion) as of July 2007.
