The head of the body that oversees China's biggest state companies has vowed to improve supervision of their overseas operations following a $550m trading scandal at the Singapore arm of the government's aviation oil monopoly.

"Major events in the last two years have shown there are still considerable gaps in central state enterprises' risk prevention and control systems," official media yesterday quoted Li Rongrong, head of the State-Owned Assets Supervision and Administration Commission (Sasac), as saying.