U.S. President Donald Trump is "closing the door" on people fleeing Islamic State, and may try to re-open secret detention centers where torture can be used, Human Rights Watch (HRW) said on Wednesday, calling on Congress to intervene.

A temporary ban on refugees that Trump is expected to sign this week is a "particularly ugly" policy among a range of populist initiatives that could also breach the U.S. Constitution, the rights group said.

Trump looks set to "stop refugee admissions to the United States, ostensibly on security grounds," HRW head Kenneth Roth told a news briefing in Geneva.