The teenage Kurdish fighters who claim to have killed scores of Isis fighters

Kurdish forces have been successful in pushing back the extremist forces across the north of Syria and Iraq

Rustam Judy, leader of the group fighting Isis, is just 18 years old (Screengrab, via Sky News)

Kurdish fighters claim they have killed large numbers of Isis militants across the north of Syria.

Fighters with the YPG, a milita of Syrian Kurds all of whom are agred between 16 and 18, say they have pushed the extremist group back from the north of Syria partly aided by US-led coalition air strikes.

"We are fighting with our hearts not just with weapons because we do not have enough equipment, but it is my duty to defeat the enemy for my people and my homeland," 18-year-old leader Rustam Judy said.

As the group advanced, accompanied by Sky News, they witnessed signs of Isis’s barbarity.

Uncovering dungeons, the fighters claimed Yazidi women had been held underground by their captors inside these small rooms. On the walls, diaries purportedly written by these women showed a miserable existence.

The Yazidi minority sect has been systematically targeted by Isis, also known as either the Islamic State or Daesh, who are believed to have executed and enslaved thousands of men, women and children.

Sky News also witnessed bodies of Isis militants abandoned in shallow graves as the extremists were forced to pull back in the face of Kurdish assaults.

Progress to reclaim territory from Isis has twinned with increased coalition air strikes. On Saturday the US and its allies conducted seven strikes against positions in Syria and 15 in Iraqi territory.

The advance comes as the civil conflict in Syria shows few signs of halting, despite scheduled peace talks. International observers estimate more than 250,000 people have been killed, and as many as 12 million displaced, in a sprawling war involving numerous disparate parties.