A director of medium-sized Chinese lender the Bank of Beijing is under investigation by authorities, the firm said, the second senior banker implicated in corruption in under a week.

Lu Haijun was being probed for alleged "serious disciplinary violations", the Shanghai-listed bank said late Monday in an exchange filing.

It gave no further details, but in China the term typically refers to corruption. Lu was one of the bank's 10 directors according to its latest available earnings report, for the first half of 2014.

"The bank's operations and management are normal and the matter has no impact on the bank," the statement said.

The company's shares were down 0.20 percent at midday in Shanghai.

Lu was also former chairman of a major bank shareholder, Beijing Energy Investment Holding, according to the statement.

The announcement follows media reports that Mao Xiaofeng, president of China's largest privately owned lender Minsheng Bank, had been taken away for questioning in a corruption investigation.

Minsheng said Saturday that its operations were normal and Mao had resigned for "personal reasons".

Chinese President Xi Jinping has touted a crackdown on graft since assuming the Communist party's top post in 2012, targeting both high-level "tigers" and low-level "flies".

Earlier probes have mainly focused on government officials, but the 21st Century Business Herald reported that "the anti-graft storm is going to sweep over the financial sector".

China's oil industry was also embroiled in a corruption scandal over the past two years, leading to the downfall of Jiang Jiemin, former chairman of state-owned oil giant China National Petroleum Corporation (CNPC).