Grassroots officials remain the largest group of violators of rules requiring frugality in the expenditure of public money, the country's top anti-graft agency said.

Watchdogs investigated 3,891 cases of excessive spending nationwide in April, more than 95 percent of which involved officials at the township or section level, the basic rank of officials in China, according to the CPC Central Commission for Discipline Inspection.

The authorities punished 1,652 officials for violations. Of those, 1,549 were at township or section level, the commission said on its official website on Thursday.