The announcement of an “intentional homicide” appeared to surprise the British government, which had seemed anxious in recent weeks to distance itself from a major Chinese political scandal, saying that suspicions about the death they had passed to the Chinese were those of other Britons in China, not anything they could substantiate on their own.

After an urgent huddle with other British officials, William Hague, the British foreign minister, told reporters in London: “It’s a death that needs to be investigated, on its own terms and on its own merits, without political considerations. So I hope they will go about it in that way, and I welcome the fact that there will be an investigation.”

Xinhua’s statement appeared to confirm one of the swirling rumors in the case, that Mr. Heywood’s death was linked to business dealings gone awry. The Chinese news agency said Ms. Gu and her son, Bo Guagua, had had close relations with Mr. Heywood but later had “a conflict over economic interests.” But Xinhua did not specify how Mr. Heywood died, or what business interests were involved. The only other suspect in his death, Zhang Xiaojun, was described as an “orderly” working in Mr. Bo’s home.

The shock of the Chinese announcement — claiming that a member of the ruling elite was linked through his wife to a possible murder, and that the killing grew out of private business interests of the kind that have made many Chinese officials rich — had far-reaching implications for the way that China is governed. The impact was amplified since China is facing a once-in-a-decade shift in power this fall to a new generation of leaders. Mr. Bo, 62, had become a contender for a seat in the inner sanctum of power, the nine-member standing committee of the Communist Party’s Politburo.

A charismatic figure, Mr. Bo tried to build his political stature by taking a page from the political playbook of Mao Zedong, presenting himself as a populist attuned to the interests of ordinary people and stirring up nostalgia for the hugely destructive Cultural Revolution of the 1960s and ’70s, waged in the name of ordinary people against the Communist Party elite.

At the same time, Mr. Bo presided over a state-led economic boom in Chongqing, a provincial-level metropolitan region in southwestern China, and, detractors said, perverted the law enforcement process in what was billed as a campaign against organized crime. As the son of the legendary revolutionary leader Bo Yibo, he built a following among others with ties to Mao, as well as those unhappy with the get-rich-quick culture of recent decades — among them, top generals and unreformed leftists in the Communist elite.