But the Communist Party, which long ago decided that Mao was “70 per cent right and 30 per cent wrong”, does not allow full discussion of events and responsibility.

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Some of the worst excesses happened in Wuxuan, in the far southern region of Guangxi, where the hearts, livers and genitals of victims were cut out and fed to revellers.

Now, five decades after the declaration of the Cultural Revolution on May 16, the town has frozen yoghurt shops, men fish a river beneath mossy limestone karsts and red banners hang from trees proclaiming the ruling party’s dedication to the people.

Some residents say they have never heard of the dozens of acts of cannibalism, motivated by political hatred rather than hunger, that once stained the streets with blood.

At least 38 people were eaten in Wuxuan, a high-ranking member of an early 1980s official investigation told AFP, asking not to be named for fear of repercussions.

“All the cannibalism was due to class struggle being whipped up and was used to express a kind of hatred,” he said. “The murder was ghastly, worse than beasts.”

Scholars say the violence resulted from Wuxuan’s remote location, the ruthless regional Communist leader, poverty and bitter factionalism.

“In 10 years of catastrophe, Guangxi not only saw numerous deaths, they were also of appalling cruelty and viciousness,” the retired cadre wrote in an unpublished manuscript seen by AFP.

“There were beheadings, beatings, live burials, stonings, drownings, boilings, group slaughters, disembowellings, digging out hearts, livers, genitals, slicing off flesh, blowing up with dynamite, and more, with no method unused.”

In 1968 a geography instructor named Wu Shufang was beaten to death by students at Wuxuan Middle School. The body was carried to the flat stones of the Qian river where another teacher was forced at gunpoint to rip out the heart and liver. Back at the school the pupils barbecued and consumed the organs.

Residents of the old town say they do not know the history or meet questions with silence. The few willing to discuss the violence say memories are fading and the town is eager to escape its past.

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“Cannibalism? I was here then, I went through it,” a man named Luo told AFP. But Wuxuan has developed rapidly in recent years and now, he said, that history “has no meaning”.

“This was not cannibalism because of economic difficulties, like during famine,” X.L. Ding, a Cultural Revolution expert at the Hong Kong University of Science and Technology, said.

“It was not caused by economic reasons, it was caused by political events, political hatred, political ideologies, political rituals.”

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For 15 years, rumours of the carnage in Guangxi -- which one official estimated left as many as 150,000 people dead -- rippled across China, and eventually authorities sent a group to investigate.

The report was never released publicly. The outside world only learned of the slaughter when journalist Zheng Yi smuggled documents out of China after the 1989 Tiananmen Square killings and published his book Scarlet Memorial, banned on the mainland.

More recently a senior inquiry team member has sought to spread awareness in China, but his efforts have been suppressed, he told AFP.

The cadre once wrote an article for a small-circulation liberal Chinese magazine, describing the investigation findings, and saying tens of thousands died, with more than 100 people taking part in cannibalism.

Retired regional officials responded with a written denunciation sent to top Communist bodies, accusing him of falsifying facts and demanding he submit a self-criticism, rectify his errors, and apologise personally.

“They said I was anti-party, anti-socialist, anti-Mao Zedong Thought,” he said.

In recent months he took a manuscript to a publisher, but refused to cut some passages.

“Before I retired I didn’t dare say ‘no’ to the Party,” he said.

Nowadays government control over the media and public opinion is tightening, said the cadre: “It’s absolutely clear, that to establish their own authority, they control public opinion.”

No official commemorations of the anniversary are expected.

Academic Ding said the Communist Party fears recalling the officially-sanctioned chaos and violence could undermine its legitimacy.

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“The more you talk about such things, the more current CCP leaders are worried,” he said.

The suppression of knowledge and discussion worries author Zheng, who is now a dissident living in the United States.

He said: “Because the government has never permitted a deep examination of history, it’s impossible to say that lessons have been learned.”