The Serious Fraud Office (SFO) has asked Monaco for help investigating alleged corruption in the oil industry.
It put in an urgent request for international judicial assistance in criminal matters to its government, resulting in it raiding the offices of oil services firm Unaoil and the homes of its directors.
Two media reports said that the US Justice Department and anti-corruption police in the UK and Australia had started a joint investigation into Unaoil.
It's accused of bribing company executives and Iraqi officials for at least 10 years to win contracts.
"Due to recent developments it would be inappropriate for the company to comment at this time," a Unaoil spokesman said.
The chairman of Unaoil Group, Ata Ahsani, could not be reached for comment.
A spokesman for Britain's SFO said it was "aware of the allegations" but would not comment further.