US federal immigration agents arrested hundreds of undocumented immigrants in at least four states this week in what officials on Friday called routine enforcement actions.

Reports of immigration sweeps this week sparked concern among immigration advocates and families, coming on the heels of President Donald Trump's executive order barring refugees and immigrants from seven majority-Muslim nations. That order is currently on hold.

“The fear coursing through immigrant homes and the native-born Americans who love immigrants as friends and family is palpable,” Ali Noorani, executive director of the National Immigration Forum, said in a statement.

“Reports of raids in immigrant communities are a grave concern.”

The enforcement actions took place in Atlanta, New York, Chicago, Los Angeles and surrounding areas, said David Marin, director of enforcement and removal for the Los Angeles field office of US Immigration and Customs Enforcement.

Only five of 161 people arrested in Southern California would not have been enforcement priorities under the Obama administration, he said.

The agency did not release a total number of detainees. The Atlanta office, which covers three states, arrested 200 people, Bryan Cox, a spokesman for the office, said. The 161 arrests in the Los Angeles area were made in a region that included seven highly populated counties, Marin said.

Marin called the five-day operation an “enforcement surge”. In a conference call with reporters, he said that such actions were routine, pointing to one last summer in Los Angeles under former President Barack Obama.

“The rash of these recent reports about ICE checkpoints and random sweeps, that's all false and that's dangerous and irresponsible,” Marin said. “Reports like that create a panic.”

He said that of the people arrested in Southern California, only 10 did not have criminal records. Of those, five had prior deportation orders.

Michael Kagan, a professor of immigration law at the University of Nevada at Las Vegas, said immigration advocates are concerned that the arrests could signal the beginning of more aggressive enforcement and increased deportations under Trump.

“It sounds as if the majority are people who would have been priorities under Obama as well,” Kagan said in a telephone interview. “But the others may indicate the first edge of a new wave of arrests and deportations.”

Trump recently broadened the categories of people who could be targeted for immigration enforcement to anyone who had been charged with a crime, removing an Obama-era exception for people convicted of traffic misdemeanors, Kagan said.