Kurdish fighters seized control Tuesday of a key border town from the Islamic State group, cutting a major supply line in the biggest setback yet for the jihadists in Syria.
From across the frontier in Turkey, the Kurds and allied Syrian rebels could be seen raising their banners in place of the black IS flag and taking up positions at the border post.
The capture of Tal Abyad, used by IS as a gateway from Turkey to its de facto capital Raqa city, was "the biggest setback to IS since it announced its caliphate one year ago", said Rami Abdel Rahman, the head of the Syrian Observatory for Human Rights monitoring group.
The town was a key conduit for foreign fighters and supplies into IS-held territory in Syria and for exports of black market oil from jihadist-held fields in eastern Syria.
Tal Abyad's fall was "the most significant loss for IS in Syria yet", said Aymenn al-Tamimi, an expert at the Middle East Forum research group.
The Kurdish forces and Syrian rebel allies launched a two-pronged attack on Tal Abyad on June 11, backed by air strikes by the US-led coalition fighting IS in Syria and Iraq.
They encircled the town from the southwest and southeast before capturing the border crossing just north of it on Monday.
- 'An easy win' -
The Observatory and Kurdish sources said they had seized full control of the town by early Tuesday.
"IS withdrew without much fight yesterday... It was an easy win," said Ahmed Seyxo, a spokesman for the Democratic Union Party, the political party tied to the YPG.
A spokesman for the US-led coalition praised its cooperation with Kurdish forces, noting that five strikes had been carried out near Tal Abyad on Monday.
"Our air strikes are targeting Daesh terrorists throughout Iraq and Syria," said Colonel Wayne Marotto, using the Arabic acronym for IS.
"Kurdish successes, enabled by coalition air strikes, are exposing Daesh military capabilities and terrorists for subsequent removal from the battlefield."
The battle sent thousands of terrified residents fleeing into Turkey, with the UN refugee agency saying Tuesday that some 23,000 people had sought refuge between June 3 and 15.
Refugee Khalil al-Ahmed, 55, said he was desperate to go home.
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"They take good care of us here, but I don't want any of that. All I think about is returning. It burns in my heart," he told AFP.
YPG fighters and rebel units were combing through Tal Abyad to clear mines and booby-trapped cars left behind by IS, before allowing civilians to return.
"There are mines and car bombs everywhere, and bodies of IS fighters lying in the streets," said Sherfan Darwish, a spokesman for the Burkan al-Furat rebel group fighting alongside the Kurds.
With the route from Tal Abyad to Raqa cut, IS will have to rely on border crossings much further west in neighbouring Aleppo province, adding several hundred kilometres (miles) to their supply lines, Abdel Rahman said.
IS still holds the Syrian side of the Jarablus crossing in Aleppo, which is closed on the Turkish side.
Other informal border routes remain open but none to rival Tal Abyad.
- Blow to IS morale -
Analysts said the loss of the town would be a major blow to IS morale, just as the group commemorates the first anniversary of its declaring an Islamic "caliphate".
"This is coming at a time of year when IS is trying to look as powerful as possible," said Charlie Winter, a researcher on jihadism at the London-based Quilliam Foundation.
The Kurdish victory at Tal Abyad, he said, would undermine IS's "narrative of constant divine momentum".
While the battle for the Kurdish majority border town of Kobane was in the headlines for months last year, the loss of Tal Abyad was a bigger strategic blow because IS had held it for more than a year, Winter said.
Kurdish forces now control around 400 kilometres (250 miles) of contiguous border territory from Kobane in Aleppo province to northeastern Syria, Abdel Rahman said.
Their advance has prompted criticism from Turkish officials, who fear the growing power of Kurdish forces in Syria will embolden Turkey's Kurdish minority.
Turkish officials have accused the YPG of expelling Arab and Turkmen citizens and of seeking to unite the Kurdish-majority areas of Syria.
In other developments Tuesday, government air strikes on a town in Syria's southern Daraa province killed at least 16 people, among them 13 children, the Observatory said.