At least 41 people have been killed in renewed clashes between Kurdish militias and Al Qaeda-linked terrorists.
The clashes took place in the oil-rich Hasake province in northern Syria, according to the Syrian Observatory for Human Rights.
The Observatory claimed that at least 29 Al Qaeda fighters and 12 Kurdish fighters had been killed in the clashes between the Committees for the Protection of the Kurdish People (YPG) and Islamist fighters from the Islamic State of Iraq and al-Shams (ISIS) and the Nusra Front.
The Observatory added that among the dead was a local Nusra Front commander of Egyptian origin, and claimed that the YPG had succeeded in capturing an ISIS checkpoint Tuesday.
The YPG has been engaged in a prolonged and bloody struggle for control of Kurdish-majority regions in northern Syria against Islamist groups, many of whom are linked to Al Qaeda.
Not long after the start of the uprising against the Assad regime, government forces pulled out of Kurdish areas to focus on attacks by Sunni Arab rebels against major regime strongholds.
Kurdish militias quickly moved in to take control - in particular the Kurdish People’s Defense Units (YPG) - the military wing of the People's Council of Western Kurdistan (PYD) - declaring their opposition to both the regime and the rebel movement, both of whom they say aim to continue a process of discrimination and "Arabization" against Syria's Kurdish population.
Arab and Islamist groups within the rebel Free Syrian Army (FSA) initially made a grab for Kurdish areas but were beaten back.
But the most recent clashes over the past several months have been between the YPG and Al Qaeda-linked groups, after the latter began a concerted and violent campaign to install their own independent "emirates," or Islamic mini-statelets in the oil-rich region. That was met with fierce opposition by Kurdish forces, who responded by ejecting Islamist forces from the border town of Ras al-Ain, near the Turkish border, among other areas.
Frequent battles have continued since then, amid claims of war crimes by Islamist forces against Kurdish civilians.
The PYD recently announced plans for an autonomous Kurdish region in northern Syria.
Bus bomb blast kills 21
Meanwhile, in the south of the country, a bus bomb has killed 21 people in Syria's southern Deraa province, near the border with Israel.
The Syrian Observatory for Human Rights said that "Four children and six women [were killed] in a blast that detonated as their vehicle went past Tal al-Jumua" in the Nawa area.
The bombing took place in rebel-held territory near to a besieged pro-regime outpost, and opposition activists have blamed regime forces for the attack.