National prosecuting departments investigated 24 high-ranking officials from January to November last year, including former security chief Zhou Yongkang and former vice-chairman of the Central Military Commission Xu Caihou, for alleged graft, according to the Supreme People's Procuratorate on Thursday.

"The SPP is conducting direct investigations into four of them, including Zhou Yongkang," a senior official at the SPP said, adding that they will assign other provincial-level prosecuting departments to handle the other 20 officials.

"After the investigation is over, the involved officials will face accusations including abusing power and accepting bribes," the SPP said.

The other officials under investigation include Jiang Jiemin, former director of the State-owned Assets Supervision and Administration Commission; Li Dongsheng, former vice-minister of the Public Security; Jin Daoming, vice-chairman of the Shanxi Provincial People's Congress; and Ji Wenlin, former deputy governor of Hainan.

Zhou is the highest-ranking official probed in the country's campaign against corruption since 1978 when the reform and opening-up started.

The top anti-graft watchdog announced in July that it was investigating Zhou, who retired from the Politburo standing committee in 2012.

He was arrested in December, expelled from the Party and placed under judicial investigation accused of a series of allegations including accepting bribes and "leaking State secrets".

Since November 2012, when the new leadership was elected, the battle against graft has become a top priority for the central government and the country has conducted a wide campaign to fight corruption.

Sixty-three senior officials, including four former State leaders - Ling Jihua, former minister of the United Front Work Department, Su Rong, former vice-chairman of the National Committee of the Chinese People's Political Consultative Conference, as well as Zhou and Xu - have been investigated for graft since November 2012, according to the CPC Central Committee for Disciplinary Inspection.

To tackle major corruption cases, the SPP will establish a new anti-graft department in the coming months to streamline the campaign to fight corruption, said Xu Jinhui, director of the SPP's anti-corruption and bribery bureau.

The new agency will invite a full-time member of the procuratorial committee to serve as the head of the anti-graft body, Deputy Procurator-General Qiu Xueqiang said.

"The new anti-graft authority will allow the SPP to focus on investigating major corruption cases, such as those involving ministerial and provincial level officials or above, and effectively break through some systematic obstacles in handling cases," he said.

Zhuang Deshui, a law professor at Peking University, said: "The SPP's anti-graft and bribery bureau, which was founded 20 years ago, can't meet the demand for anti-graft work."

"The new agency will concentrate its attention on investigating major corruption cases and preventing local officials from interfering in cases," he said.