Aided by informants planted in protest groups, authorities raided at least six buildings across St. Paul and Minneapolis to stop an "anarchist" plan to disrupt this week's Republican National Convention.
From Friday night through Saturday afternoon, officers surrounded houses, broke down doors, handcuffed scores of people and confiscated suspected tools of civil disobedience.
The show of force was led by the Ramsey County Sheriff's Office in collaboration with the FBI, Minneapolis and St. Paul police, the Hennepin County Sheriff's Office and other agencies.
But a St. Paul City Council member described it as excessive, while activists, many of whom were detained and then released without charges, called it intimidation designed to quash free speech.
At least five suspected leaders of the RNC Welcoming Committee, a self-described anarchist group, were taken to the Hennepin County jail, and another was being sought, said Ramsey County Sheriff Bob Fletcher.
On Saturday afternoon, he displayed a number of the confiscated items: a gun, throwing knives, a bow and arrows, flammable liquids, paint, slingshots, rocks and buckets of urine.
"We know these things were going to be used as weapons," Fletcher said, a charge protesters and their advocates vigorously disputed.
Fletcher however, stressed that he and other agencies had informants planted inside this and other groups for "a long period of time."