BEIJING, May 12 (Reuters) - China's anti-graft watchdog said it was investigating the former chairman of China state-owned giant National Chemical Corp (ChemChina), for violations of discipline and law, along with another former company official.

The investigations come after Swiss seeds and pesticides group Syngenta withdrew in March its bid for a long-delayed $9 billion IPO in Shanghai, which would have been China's largest, and one of the world's biggest, flotations this year.

Ren Jianxin, who retired from the firm in June 2018, was suspected of "serious violations of discipline and law", the Central Commission for Discipline Inspection (CCDI) said in a statement on its website on Saturday.

Dubbed an industrialist turned dealmaker, Ren, 66, served as ChemChina's chairman and party secretary from December 2014 to 2018, and was the official behind ChemChina's $43-billion bid to buy Syngenta in 2017.

The graft watchdog added that Yang Xingqiang, a former general manager of ChemChina, was also being investigated.

Yang, 57, who was general manager of ChemChina in December 2014, had worked with Ren as his assistant. In May 2021, he took up the same role at China National Salt Industry Group before stepping down in August 2022.

The watchdog gave no further details.

Chinese authorities had nudged Syngenta to withdraw its IPO application on concerns about the impact a sizeable new offering would have on a volatile market, Reuters reported last month.

The watchdog doubled down this year on a pledge to relentlessly carry out President Xi Jinping's orders to catch corrupt and disloyal officials, amid an investigation into accusations of graft surrounding military procurement. (Reporting by Ziyi Tang, Xiao Han and Ryan Woo; Editing by Clarence Fernandez)