Postings on Twitter and elsewhere show protesters unfurling a large banner that reads "No Raids" from the second floor of the building's atrium today afternoon.
A video also shows a sit-in on the marble floor near a bank of elevators. Demonstrators held signs saying "No Ban" and No Wall."
Police had no immediate information about whether there were any arrests. There was no response to a message left with the Trump Organisation.
The New York Police Department and Secret Service have beefed up security at Trump Tower since the president's election, but the atrium remains open to the public.
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