China's top prosecuting department investigated seven ministerial-level officials in the first five months of this year, an increase of 40 percent compared with the same period in 2013, according to the Supreme People's Procuratorate on Friday.

The officials include Guo Youming, former vice-governor of Hubei province, who is alleged to have taken bribes; Chen Baihuai, former deputy head of Hubei province's top political advisory body, who was suspected of abuse of power and accepting bribes; and Chen Anzhong, former deputy head of Jiangxi province's People's Congress, who is also suspected of bribery.

In addition, 1,577 officials above county level were investigated from January to May by prosecuting departments, up 33.1 percent from the previous year, according to statistics released by the SPP.

Ordinarily, when signs of corruption are discovered, the anti-graft authority will conduct a preliminary investigation. After collecting evidence it deems sufficient to support further action, it will transfer the case to the anti-corruption department under the SPP for further investigation and, if warranted, prosecution.

"Graft crimes tend to be grouped, field centralized, and regional," said Xu Jinhui, director of the anti-corruption and bribery bureau of the SPP.

He said bribery cases have seen a sharp rise, with the amount of money involved ranging from 10 million to 100 million yuan ($1.6 million to $16.1 million).

"Apart from fields such as engineering, land approval or real estate, some senior corrupt officials from State monopoly industries, including railways, electricity, petroleum and telecommunications have abused their power to help enterprises seeking illegal benefits, and accepted huge bribes," he added.

In addition, public involvement and social supervision are playing an active role, and prosecutors have been collecting valuable corruption clues from public reports, he said.

Xu said national prosecutors will place emphasis on State monopoly industries, including electricity, petroleum, minerals and telecommunications, while intensifying supervision of other key investment areas, such as water conservation, environmental protection, new energy and financial sectors.

Meanwhile, anti-graft authorities will pay more attention to the promotion of officials, and intensify supervision of the election of legislators and political advisers for government service at each level, he said.

Tian He, a law professor from the Chinese Academy of Social Sciences, said the central government has used legal means to fight corruption, and the crackdown has been consistent, a clear sign that corrupt officials should not bet on their ability to avoid punishment.