Disgraced Chinese politician Bo Xilai has been formally expelled from the ruling Communist Party, state media said Sunday, in a decision made at a meeting of top party officials that ended just days ahead of a broader once-a-decade power handover.

The ouster, which clears the way for Bo to face criminal trial, came at a gathering of 500 top party officials that wrapped up in Beijing. The ten-yearly leadership transition, scheduled for a party congress that opens Thursday, had been dogged by the Bo scandal.

The party's Central Committee "endorsed a decision by the Political Bureau ... to expel Bo Xilai", Xinhua news agency said -- referring to the party's top 25-member policy-making body -- adding it had taken the decision last month.

The months-long controversy surrounding Bo had exposed deep divisions in the top leadership, as he had influential patrons and a following among left-leaning members, ahead of the sensitive power transition.

The former party boss in the central mega-city of Chongqing was once seen as a candidate for promotion to the party's top echelons but was brought down earlier this year by murder allegations against his wife that came to light after his police chief sought refuge in a US consulate.

Gu Kailai, Bo's wife, was later given a suspended death sentence -- a judgment commonly commuted to a life sentence -- for fatally poisoning British businessman Neil Heywood.

Xinhua said previously that Bo had "borne major responsibility" in connection with the murder of Heywood and would "face justice" for alleged abuse of power, taking "massive" bribes and having inappropriate sexual relations.

Late last month he was expelled from the country's parliament and stripped of his legal immunity.

The committee during its four-day meeting also agreed to expel former railways minister Liu Zhijun, who was sacked last year for allegedly taking more than 800 million yuan ($128 million) in bribes and awaits trial.

Appointed in 2003, Liu was accused of taking the payouts while doling out contracts for the rapid expansion of China's high-speed railway system, which has been plagued by graft and safety scandals.

Separately, the committee named generals Fan Changlong and Xu Qiliang as vice chairmen of the Central Military Commission, following recent leadership reshuffles including a new air force chief and army deputy chief of staff.

The committee also approved a draft amendment to the party constitution, Xinhua reported without giving details.

China analyst Joseph Cheng said more critical but non-publicised decisions at the gathering likely had to do with finalising leadership positions, whose appointments the congress of about 2,000 party members will approve.

Vice President Xi Jinping is set to succeed outgoing President Hu Jintao, while Vice Premier Li Keqiang is expected to replace outgoing Premier Wen Jiabao.

But little else is known about who will fill the supporting cast, including in the Politburo and its Standing Committee, the nation's top decision-making body, which is expected to have five to seven members besides Xi and Li.

Observers have said that Bo's fate served as a bargaining chip for rival factions seeking their preferred candidates for top spots.

"The situation has certainly not been very satisfactory in that the bargaining goes on till the very end," said Cheng, a professor at Hong Kong City University. "It should be finalised by now."

Authorities had hoped for a smooth build-up to a congress that is tightly scripted to underline the party's claim to be the only legitimate force capable of ruling the world's most populous nation.

But the party has instead been rocked by the Bo case and the details of murder, bribery and the affluent lifestyles of the party power elite that it laid bare.

In the days leading up to the gathering, which typically lasts one week, already strict censorship of the media and Internet has been further tightened while security personnel have flooded cities.

More than 1.4 million people in Beijing have volunteered to help police "maintain stability", Xinhua reported.