The US has arrested 74 people including nearly 30 in Nigeria, as part of an effort to combat email scam artists.
It said the arrests reflect a coordinated crackdown on people who convince correspondents to wire them money for fraudulent activities.
The US said such scams are "prevalent" and pledged to pursue perpetrators "regardless of where they are located".
Authorities said they have seized, recovered or disrupted more than $16m (£12m) since January.
The effort, which involved local and federal law enforcement agencies, targeted scammers who trick people into transferring them money, for example by impersonating a business partner or colleague.
In one case, the US alleged that two Nigerians living in Dallas posed as a property seller when requesting a $246,000 wire transfer from a real estate attorney.
Authorities also went after "money mules" - "witting or unwitting accomplices" who receive the money from the victims and transfer it as directed by the fraudsters.
'Disrupt and dismantle'
The US said arrests occurred in the US, Nigeria, Canada, Mauritius and Poland.
One man was extradited from the UK in 2016 for his role in a scheme that allegedly sought to take $2.6m. He pleaded guilty in January to wire fraud and identity theft.
FBI Director Christopher Wray, whose agency funded and coordinated the operation, said: "This operation demonstrates the FBI's commitment to disrupt and dismantle criminal enterprises that target American citizens and their businesses."
The FBI said people have reported losing more than $3.7bn since it started tracking the issue through its Internet Crime Complaint Center.
"The devastating effects these cases have on victims and victim companies, affect not only the individual business but also the global economy," the US said.