The Kurdish-led Syrian Democratic Forces fully withdrew from a Turkish-encircled town in northern Syria on Sunday, in what appeared to be the start of a wider pullout under a ceasefire deal.
Ankara launched a cross-border attack against Syria's Kurds on 9 October after the United States announced a military pullout from the war-torn country's north.
A US-brokered ceasefire was announced late Thursday, giving Kurdish forces until Tuesday evening to withdraw from a buffer area Ankara wants to create on Syrian territory along its southern frontier.
The deal requires the SDF -- the de facto army of Kurdish authorities in north eastern Syria -- to pull out of the border zone extending 32 kilometres (20 miles) deep into Syrian territory, the length of which is not clear.
The Kurds have agreed to withdraw from an Arab-majority stretch of border from Tal Abyad to Ras al-Ain, around 120 kilometres (70 miles).
But Turkey ultimately wants a much longer "safe zone" to stretch 440 kilometres along the frontier.
On Saturday, SDF commander Mazloum Abdi said Kurdish forces would withdraw from the 120-kilometre zone as soon as they were allowed out of Ras al-Ain, which was besieged by Turkey's troops and Syrian proxies.
The SDF later said its fighters had completely evacuated the border town as part of the truce agreement, after Turkey's defence ministry confirmed they were departing.
An AFP reporter on the ground saw at least 50 vehicles, including ambulances, leaving the town hospital, from which flames erupted shortly after their departure.
Dozens of fighters in military attire left on pickups, passing by checkpoints manned by Ankara-allied Syrian fighters, he said.
US troops withdraw
In the town of Tal Tamr, Samira, 45, was among women and men carrying SDF flags awaiting the convoy from Ras al-Ain.
"I can't believe Sari Kani has fallen," she said, using the Kurdish name for Ras al-Ain.
"We're saluting our fighters who defended us, though the great powers betrayed our people," she told AFP.
Earlier this month, US president Donald Trump announced the withdrawal of US special forces from northern Syria in what was widely seen as betrayal of the Kurds and a green light for a Turkish attack.
The Kurds have been a key ally to Washington in the US-backed fight against the Islamic State group in Syria, but Turkey views them as "terrorists" linked to Kurdish militants on its own soil.
A week ago, the Pentagon said Trump had ordered up to 1,000 troops out of northern Syria.
Earlier Sunday, US forces withdrew from their largest base in northern Syria, the Observatory said.
The correspondent in Tal Tamr saw more than 70 US armoured vehicles escorted by helicopters drive eastwards on the highway, some flying the American flag.
The Observatory said the convoy was evacuating the Sarrin military base on the edge of the planned buffer zone.
Sunday's pullout, the fourth such withdrawal of American forces in a week, left Syria's northern provinces of Aleppo and Raqa empty of US troops, Abdel Rahman said.
Since 9 October, Turkish-led bombardment and fire has killed 114 civilians and displaced at least 300,000 people from their homes, the Observatory says, in the latest humanitarian crisis in Syria's eight-year civil war.
More than 250 SDF fighters and 190 pro-Ankara combatants have lost their lives, it says.
Ankara says it has lost five soldiers.
On Sunday, the Observatory said pro-Ankara fighters executed three civilians who were hiding in an industrial part of Ras al-Ain.
On Twitter, Trump cited defence secretary Mark Esper on Sunday as saying the ceasefire was "holding up very nicely".
"There are some minor skirmishes that have ended quickly. New areas being resettled with the Kurds," he said.
The Kurdish authorities in north-eastern Syrian said they were "perplexed" by Trump's statement on a successful truce.
"Turkey and its mercenaries have absolutely not abided by it and repeatedly violated it," they said in a statement.
"Trump saying the Kurds have been resettled in new areas opened the way to ethnic cleansing," it warned, calling for international protection for the displaced.
International observers have warned that Turkey's incursion could force Kurdish fighters to redeploy from prisons and camps where they are guarding thousands of suspected IS fighters and family members, making way for jailbreaks.
That has raised fears of a resurgence by the extremists, whom the SDF expelled from their last scrap of territory in March but who continue to claim deadly attacks in Kurdish-held areas.