Britain said Monday it had asked Chinese authorities to investigate the death of a British businessman in Chongqing, a sprawling metropolis at the heart of China's biggest political drama in years.

"Some time after the death of Neil Heywood we became aware of speculation about aspects of the case that may warrant further investigation," John Gallagher, spokesman for the British embassy in Beijing, told AFP.

"This is a matter for the Chinese authorities. We have raised concerns with them and have asked them to investigate thoroughly."

He gave no further details on Heywood or the nature of his business in the southwestern city of Chongqing, but there has been speculation among Chinese netizens the British national died in November in suspicious circumstances.

There have also been rumours that Heywood was linked to Bo Xilai -- a prominent Chinese politician who was sacked more than a week ago as party chief of Chongqing, in a dramatic event still shrouded in mystery.

Bo was ousted just weeks after Wang Lijun -- his former police chief and right-hand man -- fled to a US consulate and reportedly demanded political asylum, in what was a major embarrassment for the ruling Communist Party.

Wang has since been placed under investigation, but the reasons behind his reported attempted defection are still unclear.

Bo was a rising party star and until his sacking, the 62-year-old was widely touted as a favourite to join the country's most powerful decision-making body during a key leadership transition later this year.