Zhang Zhirong, one of China’s richest men, has abruptly resigned from his post at the helm of shipbuilding empire Rongsheng Heavy Industries.

Mr Zhang was at the centre of a probe this year by the US Securities and Exchange Commission concerning alleged illegal insider trading in shares of Nexen, the Canadian energy group, by Well Advantage, a company he controlled. Nexen is being acquired by Cnooc, the Chinese state-owned oil group.

Rongsheng, the shipbuilding group, yesterday said Mr Zhang was stepping down as chairman “to devote more time to his personal endeavours”, according to a statement posted on the Hong Kong stock exchange. Mr Zhang also announced he was stepping down as chairman of Glorious Properties, a Hong Kong-listed real estate company he controls.