For more than a year, the Islamic State group and Kurdish militias have been locked in a fierce fight in several pockets of northern Syria where large Kurdish populations reside.
The clashes are but one aspect of Syria's broader civil war, a multilayered conflict that the UN says has killed more than 190,000.
Since yesterday, Islamic State militants appear to have gained the upper hand in Syria's northern Kurdish region of Kobani, also known as Ayn Arab, overrunning 21 Kurdish villages, the Britain-based Syrian Observatory for Human Rights said.
Nawaf Khalil, a spokesman for Syria's powerful Kurdish Democratic Union Party, the Kurdish fighters withdrew or lost up to 20 villages in the Kobani region and evacuated civilians with them.
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"The battles that are taking place in Kobani are the most violent," Khalil said adding that Islamic State group fighters were using tanks in their offensive. Khalil called on Kurds around the world to come to Syria to defend Kobani.
The fighting forced nearly 3,000 people to try flee to Turkey and gathered near the border Turkish district of Suruc, according to the private Dogan News Agency.
Like many fronts of Syria's civil war, momentum in the fight between the extremists and the Kurds has swung back and forth. Earlier this week, for example, Kurdish fighters captured 14 villages from the Islamic State in other parts of Syria.
Still, the retreat in Kobani marked a setback for the battle-hardened Kurdish force known as the People's Protection Units. The militia, which also goes by the initials YPK, has been perhaps the most successful fighting force battling the Islamic State group, which has routed Iraqi and Syrian government forces.