Former rising Chinese political star Sun Zhengcai has been expelled from the ruling Communist Party and dismissed from public office amid a corruption investigation.

Sun, the former top official in the mega-city of Chongqing, is the highest-ranking serving official to be ensnared by President Xi Jinping's sweeping anti-corruption campaign, now in its fifth year.

The official Xinhua News Agency said the party's Politburo had approved the latest actions against Sun at a meeting Friday after reviewing a report from the investigation. That comes just three weeks before a major party congress held once every five years.

The moves clear the way for Sun to be prosecuted, with a guilty verdict all but certain. The party has said only that Sun is accused of "serious violations of discipline," shorthand for corruption.