The Xinhua editorial was published soon after Li Changchung, a Chinese official, met in London with British Prime Minister David Cameron and Foreign Minister William Hague, CNN reported. Hague said in a statement the British government wants a complete investigation that "is free from political interference."
Neil Heywood, 41, was found dead in a hotel room in Chongqing in November. The death was initially believed to have been from alcohol poisoning but has since been linked to Bo Xilai, the former Communist Party chief in Chongqing.
Bo's wife was arrested last week on suspicion of homicide, and Bo was suspended from the party's central committee.
Wang Lijun, Chongqing's former police chief, tried to get asylum in a U.S. consulate in February and was then detained by state security police, the report said.
"Based on the facts made public so far, the Wang Lijun incident is a serious political event that has created an adverse influence both at home and abroad, the death of Neil Heywood is a serious criminal case involving the kin and aides of a Party and state leader, and Bo has seriously violated Party discipline," Xinhua said.
The central committee has made "a resolute decision to thoroughly investigate related events and release information in a timely manner," the agency also said.
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