Immigration officials arrested hundreds of people across the country last week in what appeared to be a crackdown on illegal immigration prompted by President Donald Trump, although federal officials said the operations were planned weeks before the president took office.

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U.S. Immigration and Customs Enforcement agents targeted "immigration fugitives, re-entrants and at-large criminal aliens" last week as part of a "targeted enforcement operation," according to ICE officials. More than 600 people were arrested in at least 11 states, The New York Times reported.

Those detained included nearly 200 people apprehended in the Carolinas and Georgia, more than 150 in southern California and about 40 in New York, according to ICE officials.

Trump took credit for the raids on Sunday, writing on Twitter that "the crackdown on illegal criminals is merely the keeping of my campaign promise."

A Salvadoran gang member and a Brazilian drug trafficker were among those apprehended, The Associated Press reported.

However, ICE officials told multiple news agencies that the immigration operations were planned before Trump took office.

An ICE official who spoke to The New York Times on the condition of anonymity told the newspaper that the state's operation was "part of a national action that was planned several weeks ago," and focused on specific people.

"All these people are in violation of some sort of immigration law," the unidentified official told The New York Times. "We're not going out to Walmart to check papers — we know who we are going out to seek."

David Marin, ICE's field office director for enforcement and removal operations in greater Los Angeles, told the AP that the California operation was in its planning stages "before the administration came out with their executive orders."

Trump signed a sweeping executive order in his first days in office that expanded on the groups of illegal immigrants whose deportations would take priority and to bolster the number of agents on the southern border.