BEIJING (Reuters) - China will prosecute a former high ranking official in its secret police for suspected bribery, the state prosecutor said on Monday, taking a step that will almost certainly result in a conviction.

Ma Jian, once a vice minister at China’s Ministry of State Security, is the most senior security official to be investigated since former domestic security tsar Zhou Yongkang was ensnared in a graft scandal and jailed for life in 2015.

Ma, who was put under investigation in January 2015, was expelled from the party in December after it accused him of abuse of power, taking bribes and interfering in unspecified law enforcement activities.

In a brief statement, the state prosecutor said that Ma was suspected of taking bribes and it had formally started proceedings against him. It has also approved “coercive measures”, a Chinese legal term that generally means detention.

It gave no other details.

As the party controls the legal system the courts will not challenge its accusations, giving Ma little chance of acquittal.

It was not possible to reach Ma for comment and unclear if he has been allowed to retain legal representations.

Dozens of senior officials have been investigated or jailed since President Xi Jinping assumed power four years ago, vowing to root out corruption, warning, like others before, that the problem threatens the Communist Party’s grip on power.

The powerful state security ministry is a KGB-like operation that spies on its citizens and foreigners domestically and internationally. It is one of the most opaque agencies in China and does not have a public website or spokesperson.

A source with ties to the leadership has previously told Reuters that Ma was director of the ministry’s “No.8 bureau”, which is responsible for counter-espionage activities, keeping a watch on foreigners, mainly diplomats, businessmen and journalists.

Ma worked at the spy agency for more than 30 years and was closely tied to Ling Jihua, a one-time senior aide to former President Hu Jintao, according to the Hong Kong-based South China Morning Post.

Ling Jihua was jailed for life last July.