Anti-graft authorities investigated more than 60,000 cases in the first five months of this year, nearly 35 percent more than in the same period last year, according to an official from the top anti-graft watchdog.

The increasing number of cases investigated reflects the anti-graft authorities' firm resolve to fight corruption, said Xie Guanghui, deputy director of the clean-governance research center at the Communist Party of China Central Commission for Discipline Inspection.

Xie made the remarks during an online interview held by the commission on Monday.

Many senior officials were been found to be occupying several public apartments, to have bought government vehicles of a higher standard than authorized, to have played golf with public funds and to have violated frugality rules on traveling overseas at public expense, said Xie, who has worked at the commission for 12 years.

He said supervision of senior officials will be enhanced amid the anti-graft campaign launched in late 2012 when the Party's new leadership was elected.

The commission has announced corruption investigations into 18 senior provincial-level officials and two top national-level leaders this year. Last year, 17 officials of similar rank were investigated.

In the latest case, on July 20, Wu Changshun, head of Tianjin municipal public security bureau, was placed under investigation.

Leng Baoqing, a publicity official at the commission, said some senior officials accepted bribes through other methods, making it difficult for anti-graft officers to supervise them.

For example, Ni Fake, former vice-governor of Anhui province who was investigated last year, nominated himself as honorary president of the provincial jewelry association and allegedly accepted jade worth 12 million yuan ($1.94 million).

"Ni said collecting jade was his hobby, but it turned out to be a backdoor way to take bribes," Leng said.

anbaijie@chinadaily.com.cn