BEIJING (REUTERS) - Three more officials with China's leading oil firm, the China National Petroleum Corporation (CNPC), have been put under investigation for "severe breaches of discipline", China's state-owned asset watchdog said on Tuesday.

The State-Owned Assets Supervision and Administration Commission said group vice-president Li Hualin, vice-president of listed company PetroChina, Mr Ran Xinquan, and PetroChina chief geologist Wang Daofu are all under investigation.

PetroChina said in a filing to the Hong Kong stock exchange that the three had all resigned. The company's shares were suspended from trading earlier on Tuesday pending an announcement.

On Monday, China's Ministry of Supervision announced that another CNPC vice-president Wang Yongchun had been put under investigation for disciplinary breaches, without going into further detail.

A CNPC spokesman said Mr Wang had also resigned.