BEIJING (REUTERS) - China's anti-graft watchdog is investigating events surrounding a boozy small-town banquet at which one official "drank himself to death", the agency said in a statement.

Lavish banquets, where tables are often piled high with expensive rice liquor and exotic delicacies, are both a frequent indulgence for China's elite and a symbol of government excess.

The Central Commission for Discipline Inspection is investigating Mr Chen Ruixi, deputy mayor of the small city of Sanming in coastal Fujian province, who attended the banquet, as well as his colleagues.

One official died suddenly after the feast, held at the canteen of a private company, the agency said, adding that the event had made a "negative social impact".

China's President Xi Jinping has vowed to pursue both high-flying "tigers" and lowly "flies" in his campaign against pervasive graft - but critics say it's mostly the "flies" who have been taken to task.

Local party authorities have already given Mr Chen a "serious warning", the agency said, along with colleagues who joined in the revelry.

The banquet was organised so that Mr Chen and officials of the unnamed business could thrash out an investment deal, it added.

Graft oils the wheels of China's government at every level, and Mr Xi has made the fight against corruption a central theme.

However, critics say real results are impossible without meaningful reform and steps to increase transparency.

On Sunday, China sentenced a prominent activist for government transparency to four years in prison, in a case that critics say underscores the limits of the campaign against graft.