The Islamic State group launched a major offensive Wednesday against the Syrian border town of Ras al-Ayn. The assault on the strategically located town sparked fierce clashes with Kurdish militias in the area, leaving dozens dead on both sides, Agence France-Presse reported.

Fighters from the Islamic State group (ISIS) started a huge assault towards Ras al-Ayn, and were able to take over a village nearby, the U.K.-based Syrian Observatory for Human Rights told AFP. Ras al-Ayn and its surrounding towns are under the control of the Kurdish People’s Protections Units (YPG) militia, which confirmed the offensive.

A Kurdish official said the assault by Islamic State group fighters, supported by heavy weapons and tanks, had forced YPG forces to withdraw from a nearby village. “There are martyrs and dead. but the number of martyrs is unknown so far,” a representative of the Kurdish-run defense council in the area told Reuters.

Hundreds of Islamic State group fighters participated in the attack, which appears to be an attempt to retake the initiative from the Kurdish forces who have made territorial gains against the extremist group in northeastern Syria in recent weeks. Kurdish fighters have been among the most prominent local forces engaged in the battle against the militant organization, which seized significant swathes of territory in Iraq and Syria last summer.

The Islamic State group was forced to retreat from the key border town of Kobani in January after an intense assault by YPG fighters backed by U.S.-led coalition airstrikes. The air campaign encompassed more than 700 airstrikes against ISIS targets in the city, with more than 1,000 militants estimated to have been killed in the battle, the New York Times reported. The struggle over Kobani became a major symbol of resistance in the war with the Islamic State group, and U.S. Secretary of State John Kerry later characterized the victory as a “big deal” in the effort to combat the militant group.

The U.S.-led coalition said Tuesday the Islamic State group had lost control of territory near the town of Tel Hamis in Syria last week, according to Reuters. As a result, the militant organization no longer had “access to primary travel routes historically used to move its personnel and materials into Iraq -- namely Tal Afar and Mosul.”