Kurdish fighters on Thursday captured the Syrian border town of Ras al-Ain and moved east to oil and gas fields, causing an electric blackout in parts of Syria.
Although fighting in Ras al-Ain has reportedly subsided, the UK-based Syrian Observatory for Human Rights said the violence took at least 29 lives.
The Kurdish rebels proceeded to attack gas and fuel pipelines east of Ras al-Ain, cutting off electricity in several parts of Syria, according to Syria's official news agency SANA.
The attack by the Kurdish-Syrian Democratic Union Party (PYD), a group Turkish authorities describe as a separatist terrorist organization, "rang alarm bells in Ankara," Reuters said. Turkey has been battling a Kurdish militant insurgency for decades.
The taking of the rebel-held Ras al-Ain reflects the growing complexity of the war in Syria, in which an estimated 100,000 people have been killed in more than two years of fighting between President Bashar al-Assad's regime and an armed rebellion.
The PYD also reportedly seized the border crossing from Syria into Turkey after defeating fighters from Jabhat al-Nusra, a Syrian rebel group with ties to Al Qaeda, that had been in control of Ras al-Ain.
Power went out in the Syrian provinces of Dara’a, Sweida, Quneitra, Damascus and Rif Dimashq, SANA said, according to Iran's Press TV.