The security video looked like a scene from an undercover sting operation against a 30-year-old Turkish graduate student in her white coat and backpack.

Rumeysa Ozturk was walking down a street in Somerville, Mass., on Tuesday when she was surrounded by federal agents wearing dark sweatshirts, some of their faces obscured by black masks. As they pulled off her backpack and handcuffed her, the terrified student let out a cry. One officer explained, “We’re the police.”

As the Trump administration ramps up its deportation efforts, critics say tourists, foreign students and other legal immigrants are being subjected to aggressive arrest tactics usually reserved for criminal suspects. They have been swarmed by teams of masked agents in masks, zip-tied and bundled into unmarked vehicles.

The tactics are not particularly new. U.S. Immigration and Customs Enforcement officials declined to answer questions about tactics on Thursday, but former officials said federal immigration agents do wear street clothes to avoid giving away their presence before an arrest. They also can wear face coverings to avoid being singled out and doxxed online.

Deborah Fleischaker, a former ICE chief of staff under the Biden administration, said that plainclothes ICE agents have long been allowed to detain undocumented immigrants, though they are required to show their badges when making such arrests.

What is shifting are the targets — immigrants with valid visas and legal status. In Ms. Ozturk’s case, supporters say she appears to have merely been a co-author of an editorial in a student newspaper criticizing Tufts’s support for Israel.

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