Corruption charges against disgraced Chinese politician Bo Xilai will date back to an earlier stage of his career, media reported Tuesday -- a narrow focus that could help contain political fallout from the case.

The downfall of Bo -- who ran the megacity of Chongqing and sat on the ruling Communist party's 25-member Politburo -- marked China's biggest political scandal in decades.

His glittering career came crashing down amid allegations that his wife -- later convicted of murder -- was involved in the death of a British businessman and he had sought to block the police investigation.

More than a year after the scandal broke, Bo was indicted last week for embezzlement, bribery and abuse of power, the official Xinhua news agency reported.

But according to a report Tuesday from the respected current affairs magazine Caijing, the 25 million yuan ($4.1 million) corruption charges against Bo stem from his time running the smaller city of Dalian in the 1990s, not Chongqing. It did not cite a source.

Analysts say given the length of his career and the high positions he reached it seemed implausible corruption would only affect Bo's earlier, less-powerful posts.

"When he was in Dalian he was able to take 25 million, could he possibly have stopped?" said China politics expert Steve Tsang, of the University of Nottingham, calling the concept "just not logical."

But minimising the scope of charges avoided implicating others, exposing too much high-level corruption or requiring a tougher sentence, he added.

"They want to make sure the Bo Xilai case can be managed in a way that is least damaging to the party," Tsang said.

Analysts say determining how to handle Bo's trial would have required tough negotiations among the political elite, which can effectively dictate judicial proceedings.

From Dalian -- a city of seven million people -- Bo went on to run the national ministry of commerce and then Chongqing metropolis with a population of 30 million.

The final accusation -- abuse of power -- relates to his attempt last year to stop his Chongqing police chief Wang Lijun investigating the role of Bo's wife Gu Kailai in the death of British businessman Neil Heywood, Caijing said.

Fearing retribution from his boss, Wang fled to a US consulate in the city of Chengdu in February 2012, revealing the tangled situation.

Bo was detained a month later and Gu was handed a suspended death sentence in August for murder.

China's President Xi Jinping has pledged a crackdown on rampant official corruption, but analysts doubt how effective it can be without upending powerful vested interests.

Western media last year revealed that Xi's family has amassed hundreds of millions of dollars in assets and former Premier Wen Jiabao's relatives had control of up to $2.7 billion, although neither leader was linked with corruption.