Federal immigration agents flooding U.S. streets are using a new surveillance tool kit whose increasing use on observers and bystanders is alarming civil liberties advocates, lawmakers and activists.

The force said the trial will test how the technology operates in a “railway setting” and follows months of planning and research aimed at improving public safety. The operation began at London Bridge ...

Luis Martinez was on his way to work on a frigid Minneapolis morning when federal agents suddenly boxed him in, forcing the SUV he was driving to a dead stop in the middle of the street. Masked agents ...