US authorities arrested 538 illegal migrants and deported hundreds in a mass operation just days into President Donald Trump's second administration, his press secretary said late Thursday.

"The Trump Administration arrested 538 illegal immigrant criminals," Karoline Leavitt said in a post on social platform X, adding "hundreds" were deported by military aircraft.

"The largest massive deportation operation in history is well underway. Promises made. Promises kept," she said.

Trump promised a crackdown on illegal immigration during the election campaign and began his second term with a flurry of executive actions aimed at overhauling entry to the United States. 

He has signed orders declaring a "national emergency" at the southern border and announced the deployment of more troops to the area while vowing to deport "criminal aliens." 

Early on Thursday, Newark city mayor Ras J. Baraka said in a statement that Immigration and Customs Enforcement (ICE) agents "raided a local establishment... detaining undocumented residents as well as citizens, without producing a warrant". 

Earlier in the week the Republican-led US Congress green-lit a bill to expand pretrial incarceration for foreign criminal suspects.