WASHINGTON (AFP) - President Donald Trump has authorised US$4.5 million (S$6.1 million) in aid for Syria's White Helmets group, famed for rescuing wounded civilians from the frontlines in the civil war, the White House said on Tuesday (Oct 22).

Trump ordered the funds for what is formally known as the Syria Civil Defence group "to continue United States support for the organisation's important and highly valued work in the country," spokeswoman Stephanie Grisham said in a statement.

The White Helmets have received global recognition for dashing into heavy bombing to pull victims from the rubble and get them to hospitals, which themselves have frequently been bombed or shelled.

The Syrian military, which is backed by Russia, has repeatedly targeted White Helmets activists, saying they are not independent but support anti-government insurgents.

Trump's humanitarian gesture came amid a firestorm of criticism at home and abroad over his abrupt decision to withdraw a small but politically signficant contingent of US troops from Kurdish areas near Syria's border with Turkey.

The withdrawal effectively opened the door for Turkey to launch a cross-border operation against the Kurds.

Turkey sees them as a security threat but until now they had been a crucial ally of the US troops in fighting militants with the Islamic State movement.