US President Donald Trump signed a revised ban on travellers from some Muslim-majority nations Monday - one with a reduced scope so Iraqis and permanent US residents are exempt.

After his first wide-ranging and controversial restrictions were slapped down by the federal courts, Trump signed an order freezing new visas for Syrians, Iranians, Libyans, Somalis, Yemenis and Sudanese citizens.

The order did not affect pre-existing visas, the White House said. The measure is due to come into effect on 16 March.

Jeff Sessions, the attorney general, said the order "responsibly provides a needed pause so we can carefully review how we scrutinise people coming here from these countries of concern".

"Three of these nations are state sponsors of terrorism," Sessions added, referring to Iran, Sudan and Syria, adding that others had served as "safe havens" for terror operatives.

The US secretary of state, Rex Tillerson, said the renewed ban on travellers was "a vital measure for strengthening our national security".

"With this order, President Trump is exercising his rightful authority to keep our people safe," he said.

However, human rights groups said the order was still a ban on Muslims and would be challenged in court.

Amnesty urges #US Congress to block new #EO, calls it "inhumane, shortsighted;" and will "only intensify human rights crises" around world. — Rawya Rageh (@RawyaRageh) March 6, 2017

Omar Jadwat, of the American Civil Liberties Union, said: "The Trump administration has conceded that its original Muslim ban was indefensible. Unfortunately, it has replaced it with a scaled-back version that shares the same fatal flaws.

"The only way to actually fix the Muslim ban is not to have a Muslim ban.

"Instead, President Trump has recommitted himself to religious discrimination, and he can expect continued disapproval from both the courts and the people.