China's Communist chief Xi Jinping told top officials in the ruling party to closely watch their families, state media said Wednesday, after reports that his relations and those of other elite politicians amassed massive wealth.

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.

China Telecom chief resigns after probe announced
Shanghai (AFP) Dec 30, 2015 - The head of China Telecom, one of the country's big three telecommunications firms, has formally resigned his posts, the company said Wednesday, three days after authorities announced he was under investigation.

Chang Xiaobing had resigned as chairman, chief executive officer and executive director, China Telecom said in a statement to the Hong Kong stock exchange, where it is listed.

The ruling Communist Party's internal watchdog, the Central Commission for Discipline Inspection, said on Sunday that Chang was being investigated for "severe disciplinary violations", which typically refers to corruption.

Business magazine Caixin reported that Chang has already been detained and his "problems" relate to his tenure at China Unicom, another of the country's thee major telecom companies.

He rose to become Unicom's chairman before leaving to join China Telecom in September.

"China Unicom executives accepted money and sex in return for influencing matters such as contract negotiations with suppliers and personnel promotions," the magazine reported, but did not say whether Chang was personally involved.

China Telecom shares closed down more than one percent on Wednesday.

Since Xi Jinping took office as president nearly three years ago, China has launched an unprecedented anti-corruption campaign, which has brought down government officials and corporate executives.

The drive has targeted state-owned companies in the energy, auto and aviation sectors.