The NCA said more than 400 children had been “safeguarded” thanks to the operation.
The six-month operation, which had remained a secret until Wednesday, targeted people accessing offensive images of children online.
Arrests were made across the UK. The majority of those held had no prior contact with police. Charging decisions are awaited in most cases because of ongoing enquires.
Phil Gormley, the NCA deputy director general, said: “This is the first time the UK has had the capability to coordinate a single targeted operation of this nature. Over the past six months we have seen unprecedented levels of cooperation to deliver this result.”
Thirty-nine of those arrested were registered sex offenders.
Detectives said that one suspect was part of an online group that shared films in which he abused a child, including footage featuring “the most serious form of abuse against very young children.”
“We want those offenders to know that the internet is not a safe anonymous space for accessing indecent images, that they leave a digital footprint, and that law enforcement will find it,” Gormley said.
Officers have examined 833 properties and examined 9,172 computers, phones and hard drives.
Originally published on Voice of Russia UK.