China's former energy chief Jiang Jiemin has gone on trial for corruption, a Chinese court says.
Jiang Jiemin has been charged with bribery and abuse of power during his time at the China National Petroleum Corporation (CNPC), according to Xinhua news agency.
He was arrested in 2013, shortly after he left to head a government body overseeing state-owned companies.
China is currently conducting a widespread crackdown on corruption.
A statement on the microblog account of the Hanjiang Intermediate People's Court in Hubei province said that Mr Jiang was accused of "accepting bribes and large amounts of assets of unclear provenance, and misusing his authority as an employee of a state-owned company".
In another later statement it said that Mr Jiang pleaded guilty to the charges, and quoted him as saying he had "caused great losses to the country's assets" and "damaged the management and development of the country's oil and gas fields".
In the late 1990s and 2000s he rose through the ranks of CNPC, which is the parent company of Asia's biggest oil producer PetroChina, to become chairman.
Xinhua said he was accused of using high-level positions in CNPC between 2004 and 2013 to help others get promotions and access to projects in return for bribes.
It reported prosecutors saying that as of August 2013, Mr Jiang and his family possessed assets whose value "clearly far outstripped" what they were supposed to have, and he was "unable to give the sources" for the extra income and assets.
He left CNPC in April 2013 to take his highest position yet, as head of the State-owned Assets Supervision and Administration Commission - a Cabinet-level position.
But five months later he was fired and accused of corruption.
It is not clear how long the trial will last, but similar cases have taken only a few days.
The BBC's Celia Hatton in Beijing says that CNPC has been one of the main targets of a widespread anti-corruption campaign that has led to the arrest of thousands of Chinese government officials.
Chinese President Xi Jinping, who launched the campaign in 2012 when he took office, has warned that corruption threatens the Communist Party's grip on power.
Several top figures are either being prosecuted or investigated.
The most senior of these is former domestic security chief Zhou Yongkang, who was once a member of China's highest decision-making body, the Politburo Standing Committee. Our correspondent says that Mr Jiang is a protege of Mr Zhou.
He has been charged with bribery, abuse of power and the intentional disclosure of state secrets, state media reported earlier this month.