The Kurdish advance backed by US air raid and ground support of other rebel groups. The Kurds are advancing toward the capital of the "Caliphate". Experts: "The Islamic State is collapsing within its own strongholds."

Damascus (AsiaNews / Agencies) - The Kurdish security forces in northern Syria have captured a strategic military base, until now in the hands of the Islamic state (IS), north of the city of Raqqa, the so-called capital of the "Caliphate".

In their advanced Kurdish Popular Protection Units (YPG) were backed by US-led air strikes and other rebel groups.

This latest Kurdish military success came a week after the capture of an area bordering Turkey, long in the hands of the Islamic State. This is the border area connecting the Syrian town of Tel Abyad, with Akçakale, the first Turkish village across the border.

In their advance the Kurdish militias unearthed a tunnel of 500 meters which, once finished, would connect Tel Abyad with the first village in the Turkish border, Akçakale. Dug by the jihadists, the tunnel was one of the main routes used by fundamentalists for stocks and supplies.

Because of the heavy fighting, thousands of people poured over the border into Turkish territory.

The Kurdish security forces spokesman reported that the YPG now has complete control of the Liwa base, well within the territory controlled by the IslamicSstate. Redur Xelil adds that the Kurdish fighters are now at the entrance of Ain Issa, a town just 50 km north of Raqqa. The military base,  in the hands of IS since last year, overlooks a strategic route linking Raqqa and other jihadist outposts in the province of Aleppo to the west and Hasakah to the east.

Rami Abdel Rahman, head of the London based Syrian Observatory for Human Rights, says that sources on the ground tell them that these losses show that "the Islamic State is collapsing within its own strongholds."

The northern Syrian front is one of the few sources of good news in the context of the international military campaign against the militias of the Islamic State, considering the advance of the jihadists in many other areas of Syria and neighboring Iraq.

More than 3.2 million people have fled Syria with other 7.6 million internally displaced since the start of the uprising against President Bashar al-Assad in 2011. At least 230,000 people have died in the fighting, many of them civilians, especially in 2014. After it first emerged in 2013 in all its brutality, the Islamic State group seized large chunks of Syrian and Iraqi territories last year.

• SYRIA Raqqa
• Kurds military base war Islamic State