Fallen Chinese politician Bo Xilai admitted "some responsibility" Saturday for five million yuan ($800,000) of embezzled public funds, his first confession in a dramatic trial that has gripped millions.

Bo denies embezzling the money, intended for a local government construction project, but said: "I feel I should take some responsibility" for the money ending up in his wife Gu Kailai's bank account and for failing to investigate.

"I feel ashamed. I was too careless, because these are state funds," he said according to transcripts that the Intermediate People's Court in Jinan, eastern China, is providing on its account on Sina Weibo, a Twitter equivalent.

The courtroom scenes come after a lurid scandal triggered by the death of British businessman Neil Heywood -- for which Bo's wife Gu was convicted of murder -- that rocked the ruling Communist Party.

Until the admission Bo's performance had been defiant, denying charges of bribe-taking and embezzlement totalling 26.8 million yuan ($4.4 million).

He also denies accusations of abuse of power in connection with the investigation into Heywood's death, and pictures showed him staring at Wang Lijun, his police chief and right-hand man in Chongqing, the megacity he headed, as Wang testified in court against him.

Bo admitted making mistakes in handling the investigation into Heywood's killing, slapping Wang and sacking him as police chief after he told him Gu was responsible.

Days later Wang fled to a US consulate to seek asylum, blowing the scandal wide open, and Bo said his errors had "tarnished the reputation of the Party and the country".

"I failed to handle this incident at a critical point in a calm way and I made a serious misjudgement," he said. "I feel ashamed for this.

"I never meant to... protect Gu. I didn't mean to force Wang Lijun away."

The court transcripts are regular but delayed, and no live audio or video is available, nor are any foreign media or independent observers present in the room.

Earlier, Bo launched a scathing attack on a key witness, saying even the most stupid official knew not to discuss bribery where they could be overheard.

Wang Zhenggang, a former planning official in Dalian, where Bo was the mayor in the 1990s, told the court the politician had telephoned Gu in front of him in connection with the five million yuan.

The claim did not make sense, he said. "It is not even what the most stupid corruption offender would do. Corrupt offenders with even the lowest IQ would ask who else in Dalian was aware of the money."

The scandal erupted in advance of a generational shift of power atop the factionalised Communist Party, and Bo's generally feisty performance during his trial has astonished a public unfamiliar with the open airing of top-level intrigue.

The hearings are in stark contrast to previous Chinese political trials in which most defendants have humbly confessed their crimes amid opaque court proceedings.

Revelations of private jet flights, luxury villas and rare animal meats have held Chinese Internet users spellbound, while Bo has showed open disdain for prosecution witnesses, including Gu, whom he derided as "insane".

He confessed to having had extramarital affairs and said Gu moved to Britain because she was angry with him, the court transcripts showed.

The trial was widely expected to last only two days but will move into a fourth day Sunday, although analysts still believe a guilty verdict and long prison sentence for Bo were agreed beforehand.

Nothing has been said publicly of Bo's links with other top Communist leaders -- even though he was once head of the southwestern megacity of Chongqing and tipped to join the highest echelons of Chinese political power.

State-run media heaped praise on the proceedings, calling them a landmark in the history of Chinese jurisprudence.

"This degree of transparency has not happened before," the Global Times newspaper, which has close ties to the Communist Party, said in an editorial.

It described the Weibo postings as a "live feed" and said it "served as an important guarantee of a fair trial for Bo in accordance with the law".

"The live show has addressed various doubts and rumours in and outside China" the paper said. "It demonstrated that the authorities are ready to receive more public scrutiny."

But most Chinese-language newspapers have only carried the reports by the official Xinhua news agency, which often include only a passing mention of Bo's defence.

Xu Ming: prawn seller turned key witness against China's Bo
Beijing (AFP) Aug 23, 2013 - Bo Xilai's chief accuser at his corruption trial in China is a former prawn seller said to have made more than a billion dollars since linking up with the politician in the 1990s.

Born in April 1971 in the industrial port city of Dalian, Xu Ming spent his childhood in the countryside, the Hong Kong-based Mirror Books website said.

According to the website of Shide Group, the conglomerate Xu founded, he studied international trade at university.

His first job was a salesman in charge of Japanese clients at a prawn exporting firm in Dalian, according to Mirror Books, and he later established his own seafood trading company, although it was not a great success.

Shide Group was set up in 1992, around the same time that according to the Wall Street Journal Xu was introduced to Bo Xilai, then Dalian's mayor, and his wife Gu Kailai by a Taiwanese-American businessman, and they developed a close relationship.

The firm grew into a national conglomerate in the following eight years thanks to local government policies and contracts linked to Bo's plan to revamp Dalian into a shipping, fashion and information technology hub to impress the Party's top leadership, the paper said.

Shide now operates in sectors including construction material, petrochemical, finance, sports and home appliances.

In an example of how close Xu was to the Bo family, he accompanied Gu and her son Bo Guagua on a trip to Britain more than 14 years ago to scout out schools for the boy, according to the Wall Street Journal.

Bo is accused of accepting 20.7 million yuan ($3.4 million) in bribes from Xu, who testified for the prosecution on Thursday.

According to transcripts of evidence provided by the court trying Bo in Jinan, Xu gave the family millions over the years, including paying off a credit card bill of more than $50,000 run up by Guagua, and buying the boy an 80,000 yuan ($13,000) Segway scooter.

He said that when Gu expressed a desire to buy a villa in France, he provided $3.2 million for her to do so.

On its website Shide Group said that Xu was listed as the 85th richest person in China in 2010, worth $1.6 billion.

He faces charges of illegal business actions, the court in eastern China heard.