BEIJING—China’s antigraft watchdog detained the chairman of China Telecom Corp. , Chang Xiaobing, in the latest in a spate of moves against executives at many of the country’s top state-owned companies.

Mr. Chang was detained on suspicion of “severe disciplinary violations,” according to a one-sentence statement posted Sunday on the website of the Central Commission for Discipline Inspection, the Communist Party’s top anticorruption agency. The phrase is the agency’s byword for corruption allegations.

The statement said Mr. Chang, 58 years old, is the former chairman of the country’s second-largest mobile operator China Unicom Ltd. He assumed the top post at China Telecom in August.

The commission didn’t provide further details. A telephone message left at the communications office of China Telecom’s Hong Kong offices went unanswered. In a filing on Sunday, the company said its operations remain normal.

Calls to the executive offices of China Unicom weren’t answered Sunday. Mr. Chang couldn’t be reached.