BEIJING (REUTERS) - China's prosecutor began on Monday (Dec 11) formal legal proceedings against disgraced senior politician Sun Zhengcai, once considered a contender for top leadership, who has been accused of corruption and other crimes.

Sun was abruptly removed from his post as party chief of the southwestern metropolis of Chongqing - one of China's most important cities - in July and replaced by Chen Miner, who is close to President Xi Jinping.

Later that month, he was put under investigation and in September, the party announced he would be prosecuted for corruption. Sun was accused of leaking secrets, bribery and abusing his power.

In a brief statement, the prosecutor said that it had begun proceedings against Sun for suspected bribery and had approved the taking of "coercive measures" against him, a Chinese legal term that generally refers to detention.

The case is proceeding, it added, without giving any other details. Sun was expelled from parliament last month, removing his immunity from prosecution that he had enjoyed as a member of that body.

Chongqing is perhaps best known outside China for its association with Bo Xilai, another disgraced former party boss of the city. He, too, was once a contender for top leadership. He was jailed for life in 2013 after a dramatic corruption scandal.

It has not been possible to reach Sun or a representative for comment since he was put under investigation. It's unclear if he has been allowed to retain a lawyer.

The next likely step against Sun will be to put him on trial, where he is certain to be found guilty as the legal system is controlled by the ruling Communist Party which will not challenge the party's accusations against him.