A major Chinese telecommunications company says its chairman has resigned following an announcement that he is under investigation by the country's anti-corruption agency.

China Telecom Ltd., one of the country's three main state-owned phone companies, said Wednesday that Chang Xiaobing resigned effective immediately. Its chief operating officer, Yang Jie, was named to fill the post until a new chairman is appointed.

The Chinese anti-graft agency said Sunday that Chang was suspected of "serious violations," its term for corruption.

Dozens of executives of state-owned companies have been charged or questioned in a 3-year-old anti-corruption crackdown.