Chinese netizens on Sunday met with cynicism a high-profile investigation of the rail minister, one of the most senior officials to be probed in the government's fight against graft.

Liu Zhijun, who has headed China's railways ministry since 2003, is being investigated for alleged "severe violation of discipline," the official Xinhua news agency said -- a frequently used euphemism for corruption.

The 58-year-old has also been removed from his position as Communist Party chief of the ministry, the report said late Saturday.

"It's good news that Liu Zhijun has been detained, but it's really not enough, I hope the party will dig out the big boss behind Liu so people like me will be thankful," one online user said on sina.com's popular micro-blog.

"I see Liu Zhijun's investigation as embodying the party's inability to fight corruption," another said. "How wise the Communist Party is to let this type of degenerate become rail minister."

Liu is overseeing the ambitious development of China's huge rail network, which is expected to expand to 120,000 kilometres (74,400 miles) by 2020.

The Xinhua report, which quoted the Communist Party's discipline watchdog, did not elaborate on what Liu was being investigated for, but he is the latest high-level official to become embroiled in a graft probe.

Zhang Jingli, formerly one of four deputy heads of the State Food and Drug Administration, was expelled from the Communist Party last month. He is under investigation over alleged bribery linked to US giant Johnson & Johnson.

Corruption is widespread in China, and the nation's top leaders have repeatedly warned that it threatens the party's ability to rule.

Only last month, President Hu Jintao pledged to lead a renewed battle against graft, saying it was a source of contention among Chinese people who are growing weary of corruption scandals.

A poll of more than 850 netizens on sina.com Sunday showed 94 percent were unsurprised by Liu's investigation.

According to online users, Liu's brother Liu Zhixiang has already been jailed for corruption.

A report on the official China Court website says Liu Zhixiang, a former deputy director of the Wuhan Railway Bureau in central China, was given a suspended death sentence for crimes such as assault and bribery.