Syrian Kurdish fighters have chased Islamic State (ISIS) members from a key base north of the jihadists’ stronghold city of Raqa, a monitoring group said on Monday night, according to the AFP news agency.

The Kurdish People’s Protection Units, with air support from the United States, took complete control of the Liwa (Brigade) 93 base, according to the Syrian Observatory for Human Rights.

“IS lines of defense were pushed back to the gates of Raqa,” Rami Abdel Rahman, director of the Observatory, added.

“The Kurds also entered the outskirts of the town of Ayn Issa, close to Brigade 93… this town has basically fallen in the military sense with the capture of the base,” he was quoted as having said.

The base was important due to its position overlooking strategic roads linking Raqa to other ISIS outposts in the provinces of Aleppo to the west and Hasakah to the east, the report noted.

ISIS had held the military base after capturing it from regime forces last summer.

The taking of the base is the second blow inflicted on ISIS fighters by the Kurds in a week after the capture of Tal Abyad, on Syria’s border with Turkey.

Tal Abyad was a key conduit for foreign fighters and supplies into ISIS-held territory in Syria and for exports of black market oil from jihadist-held fields.

Kurdish forces defended the Syrian town of Kobane against ISIS in a months-long battle, and have emerged as some of the most effective forces battling the jihadist group in the year since it declared a cross-border “caliphate” with neighboring Iraq.

Cutting off supplies to Raqa is important as it is the de-facto capital of the ISIS self-proclaimed “caliphate”, established a year ago after the jihadist group seized large swathes of territory in Syria and Iraq.

Recently the group began issuing photo identity cards to males residing in the Raqa province, along with a range of administrative documents.

The jihadists have carried out numerous atrocities in areas they control, ranging from public beheadings to enslavement and mass rape.

The group has been accused of torturing and murdering prisoners, among them children and teenagers, and forcing Druze men to convert to Islam or die.

ISIS is also enforcing a strict interpretation of Islamic sharia law in the areas under its control. On Monday, for example, the group executed two youths accused of eating during daylight hours in the Muslim fasting month of Ramadan.