UN agencies on Friday appealed to Washington to continue allowing asylum seekers access to the country and to be given due process after President Donald Trump vowed to freeze migration from "Third World" countries following an attack near the White House.

The comments mark a further escalation of migration measures Trump has ordered since the shooting on Wednesday that investigators say was carried out by an Afghan national who entered the US in 2021.

Asked to respond to Trump's remarks, UN human rights office spokesperson Jeremy Laurence told a Geneva press briefing: "They are entitled to protection under international law, and that should be given due process."

UN refugee agency spokesperson Eujin Byun echoed those remarks.

"When people who need protection arrive in their territory, they have to have a due process of asylum. And then they have to have access to territory," she said, adding that the overwhelming majority of refugees are law-abiding members of the host community.

"So we really want to appeal at this point to the states who are hosting refugees and asylum seekers," she said.