BEIJING -- China's prosecutorial agencies have placed 129 officials at the prefectural level or higher under investigation for suspected corruption and bribery in the first eight months of this year, according to the Supreme People's Procuratorate (SPP).

Prosecutors across the country investigated 22,617 cases involving 30,938 people on suspicion of corruption between January and August, the SPP said in a statement on Thursday.

The number of cases was 3.6 percent higher than the same period last year while the number of people under investigation was 3.8 percent higher, and 7,080 of the cases were disclosed via tips from the public, according to the statement.

A total of 18,283 cases, or 80.8 percent, were classified as serious, an increase of 5.7 percent year on year, amid intensified anti-graft efforts, the SPP said.

The Chinese leadership has intensified anti-corruption efforts this year and vowed to go after both "tigers" and "flies," referring to high-ranking and low-level corrupt officials.

Officials put under prosecutorial investigation so far this year include Liu Tienan, former vice head of the National Development and Reform Commission; Ni Fake, former vice governor of east China's Anhui province; Wang Suyi, a Standing Committee member of the Party Committee of the Inner Mongolia autonomous region; and Li Daqiu, a senior political advisor from the Guangxi Zhuang autonomous region.

In the latest case, the discipline watchdog of the Communist Party of China said on Thursday that Ji Jianye, mayor of Nanjing, capital of East China's Jiangsu province, is currently under investigation for suspected discipline and law violations.