Pentagon, the US Department of Defense, on Sunday said upto 1,000 US troops will withdraw from northern Syria, according to news agency AFP. Hundreds of Islamic State group supporters escaped from a displacement camp in the area and there were reports of alleged atrocities amid growing international alarm.
About 1,000 troops will leave the area "as safely and quickly as possible," CBS quoted Defense Secretary Mark Esper as saying on Sunday. He added that they will not leave the country entirely.
President Donald Trump has largely stood by his decision to pull US troops back to clear the way for Turkish forces, despite growing chaos in the wake of their advance.
On Friday, US troops near the northern Syrian border came under artillery fire from Turkish positions, a Pentagon spokesman said, warning that the US was prepared to meet aggression with "immediate defensive action."
The US military confirmed an explosion around 9 pm (1800 GMT) within a few hundred meters of its post near the town of Kobani, in an area "known by the Turks to have US forces present."
"All US troops are accounted for with no injuries. US forces have not withdrawn from Kobani," Navy captain Brook DeWalt said in a statement.
Trump has faced a firestorm of criticism for appearing to greenlight Turkey's offensive into northeastern Syria, which began after Trump ordered US troops to pull back from the border.
Turkey is targeting the Kurdish-led Syrian Democratic Forces (SDF), a key US ally in the five-year battle to crush the Islamic State group. The SDF lost 11,000 fighters in the US-led campaign.
Treasury Secretary Steven Mnuchin said earlier on Friday Trump had authorised -- but not yet activated -- "very significant new sanctions" to dissuade Turkey from further offensive military action.
"The United States remains opposed to the Turkish military move into Syria and especially objects to Turkish operations outside the security mechanism zone and in areas where the Turks know US forces are present," DeWalt added.
"The US demands that Turkey avoid actions that could result in immediate defensive action."
(With agency inputs)