“For ten years, Trump has targeted me with baseless lies and smear campaigns,” Omar said in a statement.
“This is just the latest escalation in his campaign of political intimidation. I will not be silenced.”
Speaking to reporters on Monday, Trump said he had “nothing to do” with the justice department’s investigation into Omar, while describing her as a “complainer” and a “terrible person”.
The Republican president said of the Somali-born congresswoman: “She comes from a country that is a non-country.
“And then she comes over here and she complains about our Constitution.”
Omar’s communications director Jacklyn Rogers called Monday morning’s raid “an outrageous abuse of power” by the Trump administration, adding: “The Congresswoman has done nothing wrong.”
The nature of the criminal investigation remains unclear.
A BBC crew saw several agents at Omar’s home, some carrying boxes to a van.
News of the search was first reported by Fox News, which said the investigation was about immigration paperwork filed by her late father when Omar was a child.
The timing of the raid – 22 days before the November midterm elections, which will decide the balance of power in Congress for the next two years – raised concerns from Omar’s fellow Democrats.
The justice department has a longstanding policy of refraining from most enforcement action that is “likely to raise an issue or the perception” it was being brought for the purpose of affecting any election or to disadvantage a candidate.
The US House of Representatives Democratic Party leadership said in a statement that Omar had long been targeted with “vile personal attacks and baseless accusations” by Trump.
“Now, less than 30 days until the midterm election, his violent mass deportation machine has descended upon the home of a duly elected Member of Congress and her family,” it said.
Omar’s immigration records have been scrutinised in the past by Republicans. Earlier this year, fellow congresswoman Nancy Mace of South Carolina unsuccessfully filed a subpoena for her records.
Last month, Homeland Security Secretary Markwayne Mullin told a conservative podcaster “something is going to happen”, making allegations of marital fraud against Omar.
Separately, White House border tsar Tom Homan told Fox News that Omar was being investigated for unspecified immigration violations.
Omar denied these allegations last month.
“I will say it again so it’s as clear as possible: I’m not at all worried about these investigations, because they are complete shams,” she said in a campaign fundraising email.
