PetroChina, the listed arm of China's largest oil producer China National Petroleum Corp (CNPC), rejected a media report Monday that said two of its executives were under investigation for graft.

The China Business News reported that PetroChina vice president Sun Longde and director Wang Guoliang were "taken away" by authorities last Thursday.

But PetroChina said in a statement: "The news does not conform with the facts.

"The company's director Wang Guoliang and vice president Sun Longde are performing their duties as normal."

The newspaper also said CNPC planning department manager Wu Mei and two officials from another CNPC subsidiary had been taken away by authorities.

PetroChina previously announced that three executives were under investigation for alleged "discipline violations", a term that typically refers to corruption.

State media have reported that Wang Yongchun, one of CNPC's vice presidents, was also the subject of a government probe.

And Jiang Jiemin, a former CNPC chairman, is under investigation and has been removed from his most recent post as director of China's supervisory body for state-owned firms, the official Xinhua news agency said last week.

China's president Xi Jinping has vowed to crack down on corruption at all levels of the government, calling graft a threat to the future of the ruling Communist party.

Trading in PetroChina shares was suspended on Monday morning in Hong Kong and Shanghai, where the firm is listed, but resumed in the afternoon after the company issued its statement.

PetroChina closed up 2.03 percent at 8.05 yuan ($1.32) in Shanghai and rose 1.26 percent to HK$8.81 ($1.14) in Hong Kong.