BEIJING (Reuters) - Chinese media are not allowed to carry advertising which uses "extravagant wording" to promote gifts over upcoming holidays, the ruling Communist Party's anti-graft watchdog said, as the mooncake season approaches.

Since President Xi Jinping's appointment in 2013, the government has cracked down on official corruption and extravagance in China, where the flaunting of personal and often illicit wealth and wasteful public spending has led to widespread criticism of the party.

Gift giving is particularly popular over holidays, such as the Mid-Autumn Festival later this month, when mooncakes are given. The first week of October is the National Day holiday.

In a statement carried on its website late on Sunday, the Central Commission for Discipline Inspection said media needed to play its role in preventing an uptick in corruption over these holidays.

Media should go undercover to expose abuses such as using public funds to buy gifts and expose cases as soon as they come to light, it said. China has repeatedly warned against excessive gift giving.

"All media and websites must talk about politics, consider the broader picture ... and not carry or report on gift advertising that uses extravagant wording," it said.

The anti-graft campaign has over the past two years or so dragged down sales of high-end products from the fiery sorghum-based liquor, baijiu, to mooncakes, both traditional popular gifts for smoothing business and official ties.

(Reporting by Ben Blanchard; Editing by Nick Macfie)