China's Communist chief Xi Jinping has told top party officials to closely watch their families amid reports his relatives and those of other elite politicians have amassed massive wealth, state media says.

Mr Xi, who has overseen a much-publicised crackdown on corruption, told members of the party's 25-member politburo to "strictly educate and supervise their children and other family members", the official Xinhua news agency said.

Chinese officials are not required to disclose their wealth or that of their close relatives, in what critics say is a barrier to Mr Xi's anti-graft campaign.

Mr Xi has relied on internal party agencies to oversee the crackdown, while more than a dozen activists have been jailed for protesting to demand officials be made to declare their assets.

In 2012, a Bloomberg News report cited records showing that Mr Xi's family owned assets worth several hundred million dollars. China responded by blocking the company's website.

The report did not allege wrongdoing by Mr Xi, who it cited as saying in a 2004 anti-graft conference call: "Rein in your spouses, children, relatives, friends and staff."

The New York Times reported that former Premier Wen Jiabao's family had controlled assets worth $2.7 billion. China called the report a smear.

At a politburo meeting held this week, Mr Xi also urged adherence to the "three stricts and three earnests", Xinhua said.

The slogan — one of many numerical designations in Chinese politics — refers to being strict in morals, power and discipline, as well as honesty in decisions, business and behaviour.

Mr Xi has centralised power and carried out an unusually fierce campaign against allegedly corrupt officials since assuming power three years ago, although critics say it has been used for factional infighting.

Under his watch, former politburo members Zhou Yongkang and Bo Xilai have both been convicted of accepting large bribes while in office, but no systemic reforms have been introduced to promote transparency.

Animated rap video touts successes of crackdown

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The report came after Chinese state broadcaster CCTV released a video touting the achievements the country's corruption crackdown, featuring an animated, rapping Mr Xi.

The song, which pieces together Mr Xi's public speeches, extols the virtues of the now two-year-old plan.

The song proclaims that "the reform group ... has done quite a lot", according to a translation published by the South China Morning Post.

The lyrics reference one of Mr Xi's well-known statements about corruption, in which he said it was just as important to go after the "flies", or lowly people, as it was to tackle the "tigers", or top officials.

"Flies, tigers, big foxes, catch, catch, catch, catch," the song orders.

"Change the education system, change the medical system, change the household registration system, change, change, change, change!"

Xinhua said the central leading group for comprehensive reform had held 19 meetings and reviewed 102 reform documents since its establishment on December 30, 2013.

State media released an animated video promoting China's five-year plan in October, which featured an animated David Bowie.

ABC/ AFP