The three arrested men in the South West are being held on suspicion of committing computer misuse and money laundering offenses.
They are a 33-year-old-man from Charlcombe in Bath, a 30-year-old man from Lower Weston in Bath and a 37-year-old man from Staverton in Wiltshire.
The suspects in the Netherlands - two men and a woman, aged 21, 26 and 29 - were arrested on suspicion of money laundering.