The decision to banish Bo from the Central Committee and its Politburo effectively ends the career of China's brashest and most controversial politician, whose downfall has kindled ideological tension and sparked opposition from leftist sympathisers who insist he is the victim of a plot.
"Officials were told that Bo Xilai's Politburo and Central Committee memberships were suspended. He cannot attend Politiburo and Central Committee activities," said one of the sources, who was briefed on the matter.
"The Central Committee will have to hold a plenum to formally strip him of his Politburo and Central Committee memberships," added the source.
The Central Committee is a council of about 200 senior officials who meet about once a year and the Politburo is a more powerful body of about two dozen Central Committee members.
The sources, who all requested anonymity, said the ruling party had made the decision after investigating Bo, the former party chief of Chongqing municipality in southwest China, over a scandal that emerged after his vice mayor, Wang Lijun, fled into a U.S. consulate for 24 hours in February.
Wang's flight triggered a series of revelations, including questions about the death of a British businessman close to Bo's family. Bo was dismissed as Chongqing party chief in mid-March.
The party settles on a new top leadership late this year, and Bo was widely seen as pressing for a top post in the Politburo Standing Committee, the innermost core of power.
"The central leadership's decision means Bo Xilai's hopes for surviving politically are finished," said another one of the sources, who said senior government officials were told of the decision on Tuesday.
"There is also sure to be further investigation of Bo Xilai and his family," the second source said.
The brash Bo had earlier exuded ambition to enter the next Politburo Standing Committee. A party congress later this year will unveil the new leadership line-up.
"This means that Bo's political career is effectively over," said Chen Ziming, an independent political scholar in Beijing who said he had heard rumours of an impending announcement but could not confirm them.
"But a decision to formally expel him would have to be made by the full Central Committee, which would have to receive a report from the Central Discipline Inspection Commission," said Chen.
The discipline commission is an elite body that enforces party rules and investigates officials accused of corruption and other abuses.
Wang's flight to the U.S. consulate and his allegations prompted the British government to urge an investigation into the death in November of the Briton, Neil Heywood, who Wang said was close to Bo's family and had a dispute with Bo's wife, Gu Kailai.
Bo, 62, and his wife have disappeared from public view since his removal as chief of Chongqing, and they have not responded publicly to the reports. Nor has Wang, who is under investigation.
Handsome and smartly dressed in a party of bland conformists, Bo arrived in Chongqing in 2007 and promoted it as a bold egalitarian alternative model of growth for China.
He vowed to narrow the gap between rich and poor, kindling hopes among supporters that he could nudge the whole country in a similar populist direction if he entered the central leadership.