Russian forces in Syria headed towards the Turkish border Wednesday to ensure Kurdish fighters withdraw under a deal between Moscow and Ankara ousting them from the minority's entire heartland.
US President Donald Trump hailed the agreement as a "big success" and announced his administration was lifting sanctions it had imposed on Turkey after it launched its offensive against Kurdish armed groups earlier this month.
Kurdish forces, who previously controlled nearly a third of Syria, have lost almost everything under the deal, which sees Turkey remain fully deployed in an Arab-majority area that was the main target of its two-week offensive.
The agreement Tuesday in Sochi also requires Kurdish forces to pull back to a line 30 kilometres from the border along its entire length (440 kilometres), forcing them to surrender some of their main towns and crushing their dreams of autonomy.
Trump has been accused of betraying key allies in the fight against the Islamic State jihadist group.
The deal -- hailed as "historic" by Turkish President Recep Tayyip Erdogan -- quashes the Kurdish minority's dreams of a semi-autonomous region and makes way for the absorption of their de facto army into the regime's military.
Erdogan vowed that Turkey would take "the necessary steps" if promises to push Kurdish fighters away from the border were broken.
Russia's defence ministry said Wednesday a convoy of its military police had crossed the Euphrates River and "advanced towards the Syrian-Turkish border".
Under the deal, Russian military police and Syrian border guards are to "facilitate the removal" of Kurdish People's Protection Units (YPG) fighters and their weapons from within 30 kilometres (18 miles) of the Turkish-Syrian border, within 150 hours.
- 'Kill, displace and occupy' -
Russia and Turkey will then start joint patrols in two zones stretching 10 kilometres (six miles) to the east and west of Turkey's safe zone, which is about 120 kilometres long (75 miles).
That will allow Turkey to patrol with Russia in areas of Syria that were not part of its offensive.
An AFP correspondent near the border town of Kobane saw several Russian-flagged military vehicles entering the area on Wednesday.
Syrian regime troops are based in the border town.
The Syrian Observatory for Human Rights, a Britain-based war monitor, said the "safe zone" area was calm on Wednesday.
But explosions hit various parts of Syria's northeast, including the Kurdish-majority city of Qamishli and the town of Suluk in the Tal Abyad region near Turkey's border.
The car bomb in Qamishli did not cause casualties, according to the Observatory. But the blast in Suluk, controlled by Ankara's rebel proxies, killed three fighters, a rebel commander there told AFP.
It was unclear who was responsible.
Kurds staged angry demonstrations Wednesday in their de facto capital Qamishli, which is excluded from the Sochi agreement.
"This deal serves the interests of foreign powers and not the interests of the people," said official Talaat Youndes.
"Turkey's objective is to kill, displace and occupy the Kurds."
Turkey's October 9 assault was made possible by a pullback of US troops deployed along the border as a buffer force between their NATO ally Turkey and the Kurdish fighters of the SDF.
The withdrawal by their erstwhile ally left the Kurds completely in the lurch, forcing them to turn to the Damascus regime for protection from an expanded Turkish offensive.
- 'Separatist designs' -
Government forces, who are backed by the Russian military, rushed north within days, ostensibly to pin back Turkish-backed rebels but also to reclaim control of swathes of territory that the regime started leaving in 2012.
On Wednesday, regime reinforcements arrived in the Raqa and Hassakeh governorates, according to state news agency SANA.
Damascus has previously accused Kurds of treason over their alliance with Washington and repeatedly said it would eventually restore government control over all parts of Syria.
The Kremlin on Wednesday accused Washington of betraying the Kurds by withdrawing its forces and leaving allies alone in the face of a Turkish offensive.
Pentagon chief Mark Esper arrived in Baghdad for talks with his Iraqi counterpart Najah al-Shammari as Washington pulled out troops from northern Syria through Iraq.
Trump said Wednesday that a "small number" of US troops will remain at Syria's oil fields, despite the broader American withdrawal.
While they are back opposing sides, Turkey and Russia have been cooperating to bring an end to Syria's devastating war.
Tuesday's agreement said the two countries were determined "to combat terrorism in all forms... and to disrupt separatist agendas in Syrian territory".
The deal said efforts would also be launched for the return of refugees to Syria "in a safe and voluntary manner".
Ankara has said some of the 3.6 million Syrian refugees in Turkey can be rehoused inside the safe zone.