Russian forces have begun to deploy troops towards the Turkey-Syria border, as part of deal to remove Kurdish troops.
Units have already entered the two key border towns of Kobane and Manbij.
Under the deal agreed by Russia and Turkey, Kurdish fighters were given 150 hours from noon on Wednesday to pull back 30km (18 miles) along the border.
Turkish troops will continue to control an area they took during a recent offensive against the Kurdish fighters, regarded by Turkey as terrorists.
Part of Turkey’s plan is also to create a “safe zone” along the border that will house some two million of the Syrian refugees it hosts.
The Turkish offensive began after the US announced a sudden and unexpected withdrawal of its troops from northern Syria. The US troops had been supporting the Kurdish fighters, who have been allies in the fight against the Islamic State (IS) group in the region.
US President Donald Trump tweeted on Wednesday that the situation in the border area had been a “big success”, and said he would speak in detail later.
The deal was negotiated by Turkish President Recep Tayyip Erdogan and Russia’s Vladimir Putin after lengthy talks in the Black Sea resort of Sochi on Tuesday.
It was agreed that Russian and Syrian forces would oversee the Kurdish pullback in an area from the Euphrates river, just east of Manbij right up to the Iraqi border in the east.
On Wednesday, Russia’s defence ministry said its forces had crossed the river at noon (09:00 GMT) and “advanced towards the Syrian-Turkish border”.
Convoys of military police were later seen arriving in Kobane and Manbij, some 60km apart.
Both towns lie outside the area forming part of Turkey’s military operation, and Russia’s foreign ministry said on Wednesday Turkish forces would not be deployed there, according to Ria Novosti news agency.
The deal does not cover the area currently under Turkish military control – between the towns of Ras al-Ain and Tal Abyad. The Turks will be allowed to retain control there. Turkey’s military says the US has told it that all Kurdish fighters have now left that area.
It also does not include the area around Qamishli. The memorandum of understanding between Turkey and Russia makes the Kurdish-majority city an exception but gives no details as to why. -BBC