David Cameron has said he is pleased the Chinese authorities are taking action over the murder of a British businessman.
It emerged on Tuesday that the wife of a senior Communist Party official in China is being probed for the "intentional homicide" of Neil Heywood.
The 41-year-old was found dead on November 15 in Chongqing in central China.
Speaking at a press conference during a trade mission to Indonesia, the Prime Minister said: "We did ask the Chinese to hold an investigation and we are pleased that they are now doing that. It is very important we get to the truth of what happened in this very disturbing case, this very tragic case."
Mr Heywood was a friend of the family of Bo Xilai, a former rising star in Chinese politics who served as local party chief in Chongqing.
At the time, Chinese officials said the British expat died of "excessive alcohol consumption". But friends questioned this, saying the businessman was not a heavy drinker.
In February, Mr Bo's former police chief Wang Lijun sought refuge in the US consulate in China. It is thought he made a number of claims against the politician and his wife Gu Kailai, including her alleged role in Mr Heywood's death.
State media reported on Tuesday that Gu Kailai and Zhang Xiaojun, an orderly at Mr Bo's home, had been arrested.
Meanwhile Mr Bo has been suspended from the Communist party's 25-member Politburo amid allegations of "serious discipline violations".
Mr Bo, his wife and their son had been friends with Mr Heywood but had recently clashed over a financial matter, state media suggested. Mr Heywood had lived in China for 10 years and was fluent in Mandarin. He had two children with his Chinese wife. It is understood his mother lives in London.