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 Xi's anti-graft campaign.

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. Bloomberg News in a 2012 report cited records showing that 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 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, 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, Xinhua added.

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.