China is investigating China Southern Airlines Co. Chairman Si Xianmin for "serious" discipline violations, according to a statement posted on the website of the Communist Party's Central Commission for Discipline Inspection.

Si is suspected of having "severely violated the rules," the commission said in a short statement Wednesday.

China, which has been cracking down on corruption since President Xi Jinping came to power three years ago, has targeted both government officials and corporate executives in its campaign. Earlier this week, Dongfeng Motor Corp. said in a statement to the Shanghai stock exchange that Chairman Zhu Fushou was being probed for suspected discipline violations.

Attempts to reach Si were unsuccessful. Two calls after regular business hours to Xie Bing, a secretary to the airline's board, went unanswered. Calls to media relations officers Peng Jun and Sean Cui weren't answered.

China Southern, Asia's biggest airline by passengers and fleet size, said last month it had removed an executive vice president being investigated on suspicions of bribery.

The airline's shares fell 3.4 percent in Hong Kong on Wednesday, paring their gains in the year to date to 69 percent. That compares with a 14 percent increase for Air China Ltd. and a 26 percent advance for China Eastern Airlines Co. so far in 2015. The benchmark Hang Seng Index fell 2.3 percent during the same period.

China Southern's shares fell 6.8 percent to US$38.69 in New York trading on Wednesday.

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