Dawn raids have been carried out as part of an international corruption probe at a banknote printing firm.
Two men were arrested as part of investigations into alleged bribes by Securency International to officials between the late 1990s and 2009, sources said.
The Serious Fraud Office (SFO), which carried out the UK operation alongside officers from Surrey, Hampshire, Thames Valley, Cumbria and Scotland Yard, said two Britons were also held in Spain.
The raids, which also included operations in Melbourne, Australia, related to dealings with senior politicians and banking officials, the Sydney Morning Herald reported.
The SFO and the Australian Federal Police are leading the operation, involving activities of employees and agents of Securency and their alleged corrupt role in securing contracts for banknote deals.
Richard Alderman, of the SFO, said: "This is an excellent example of how anti-fraud agencies around the world are working together to fight economic crime.
"It requires much painstaking preparation to co-ordinate action like this and I am delighted that our collective hard work has resulted in successful searches in a number of jurisdictions."
The police inquiry began in May last year amid allegations that millions of Australian dollars had been exchanged in commissions to offshore bank accounts.