BEIJING - China's parliament on Friday formally dismissed the nation's railways minister after he was placed under investigation earlier this month on suspicion of graft.

The standing committee of the National People's Congress dismissed Liu Zhijun and replaced him with Sheng Guangzu, Xinhua news agency said.

Earlier this month Sheng was named as the ministry's top Communist Party official, a separate post, after Liu was sacked from that position, state press reported at the time.

Liu was placed under investigation for "severe violations of discipline", state media said, wording typically used to refer to corruption.

Liu is the highest-ranking official to be placed under investigation since former Shanghai Communist Party head Chen Liangyu was dismissed in 2006 and later convicted of corruption in a case that highlighted China's graft problem.

Media reports have suggested Liu fell foul of authorities for pursuing rapid expansion of the rail network at all costs, but gave no specifics of his alleged wrongdoings.

In a report last month, Hong Kong's South China Morning Post quoted Chinese experts as saying corners were probably being cut on rail construction quality in order to realise China's huge expansion plans.