US-backed Kurdish-led forces in Syria have said American troops have begun withdrawing from areas along Turkey's border.

This comes hours after the White House said US forces in north-eastern Syria will move aside and clear the way for an expected Turkish assault - essentially abandoning Kurdish fighters who fought alongside American forces in the years-long battle to defeat the so-called Islamic State (IS) group.

The Syrian Democratic Forces said the move comes as Turkey is preparing to attack Kurdish-held areas in north-east Syria.

The statement warns the Turkish invasion would be a blow to the fight against IS militants.

The Kurdish Hawar news agency and the UK-based Syrian Observatory for Human Rights also said American troops were evacuating positions near the towns of Ras al-Ayn and Tal Abyad on Monday.