BEIJING, Jan. 10 -- The Communist Party of China's discipline watchdog closed graft investigations into eight high-profile officials and handed over their cases to prosecutors in 2013, said a senior discipline inspector here on Friday.

The officials were Zhou Zhenhong, Liu Tienan, Ni Fake, Wang Suyi, Li Daqiu, Tong Mingqian, Yang Kun and Qi Pingjing, said Huang Shuxian, deputy secretary of the Communist Party of China (CPC) Central Commission for Discipline Inspection (CCDI) and minister of supervision, at a press conference.

Five of them were senior provincial officials, two were senior officials of central government departments while one was senior executive of a state bank.

They were among 31 high-profile officials investigated by the CCDI last year and the remaining 23 are still under investigation, including Jiang Jiemin, former head of the State-owned Assets Supervision and Administration Commission, and Li Dongsheng, former vice minister of public security, Huang said.

Last year, the Communist Party of China's discipline inspection agencies punished about 182,000 officials nationwide, 13.3 percent more than in 2012, according to Huang.

Among them, about 150,000 were subject to Party discipline punishment and 48,900 were subject to administrative punishment.

After taking the helm of the CPC in November 2012 and later as the country's top leader in March 2013, Xi Jinping vowed to fight corruption and harmful work styles, calling on the entire Party to stay on full alert, as corruption threatened the Party's survival.

"As the central leadership asked, discipline inspection agencies have put anti-corruption as a priority and worked to bring down both 'tigers' and 'flies'," Huang said.

Last year, the CCDI reorganized itself to improve efficiency and put more human resources into supervision and case investigation, he said.

The CCDI opened its official website in September and created a tip-off section on the front page to get more clues on corruption.

"We are working hard to improve the efficiency and quality of our investigations," Huang said.

Last year, the agencies opened about 172,000 cases and closed 173,000 (including those opened in previous years). The figures were 11.2 percent and 12.7 percent more than in 2012 respectively.

There were two more major changes of the missions of discipline agencies in 2013.

As the new leadership started a campaign against harmful work styles such as bureaucracy and lavishness in December 2012, the discipline agencies issued a series of detailed instructions against wrongdoings and bad behaviors.

Before the Mid-Autumn Festival and National Day holidays, the CCDI forbade officials to spend public money on expensive gifts, feasts and sightseeing tours.

Before the upcoming New Year and Spring Festival, they also banned spending public money on calendars, greeting cards and fireworks as well as stopped officials from going to private clubs.

The CCDI has regularly published a list of officials who violated these rules on its website.

According to Huang, more than 30,000 officials were caught violating rules and about 7,600 of them committed wrongdoings serious enough for punishment.

Another effective anti-graft tool was to dispatch inspectors to provincial governments, big state-owned enterprises and public institutions, Huang said.

Inspectors are sent to investigate whether senior officials are involved in bribery, embezzlement, trading power for profit and other personal favors as well as expose problems of formalism, bureaucratism, hedonism and extravagance, considered four forms of undesirable work styles by the CPC leadership, Huang said.

They collect information and report to CCDI but are not allowed to interrogate the officials in question.

Last year, the CCDI dispatched ten teams of inspectors to 20 provincial governments, big state-owned enterprises and public institutions, Huang said.

They discovered important information that helped bring down a number of corrupt officials including Liao Shaohua, party chief of Zunyi City in southwest China's Guizhou Province and Guo Youming, former vice governor of central China's Hubei Province.

"Besides finding out about corrupt officials and malpractice as early as possible, inspectors also worked to deter officials from corruption," Huang said.

While fighting corruption, the CCDI also targeted breach of duty by officials. More than 21,000 officials were held responsible for failing in their duties last year in major workplace accidents and serious pollution incidents.