Bodies and severed heads have been found in a mass grave near the "Islamic State of Iraq and Syria" (ISIS) group's last bastion in eastern Syria, Kurdish officials said Thursday (February 28th).

"A mass grave was discovered about 10 days ago in a liberated area" near al-Baghouz, said Adnan Afrin, a spokesman for the Syrian Democratic Forces (SDF).

"It contains the bodies of men as well as the severed heads of women," he told AFP.

The SDF, an Arab-Kurd alliance fighting ISIS in Syria with support from the international coalition, is days away from taking the last pocket of territory still held by the extremist group by the Euphrates river, near the Iraqi border.

Afrin said the number of bodies in the mass grave was not yet known, adding that the site was discovered by accident when a bulldozer was at work in the area.

The mass grave was found on the outskirts of al-Baghouz "in the direct vicinity of homes", Azad Dudeki, a Kurdish Red Crescent official, told Diyaruna.

It contains the remains of both men and women who were seemingly executed, he said, noting that the number of women among them is very high and most of them were beheaded, while most of the men were killed with a gunshot to the head.

"Confirmed information received in recent weeks indicate that a high number of executions were carried out against civilians who tried to leave the group’s area, or who were accused of working with international coalition forces or the SDF," Dudeki said.

A large number of ISIS elements also were executed for refusing to fight or for trying to escape from the last sliver of territory still held by the group, he added.

Yazidi victims

It is believed some of the victims could be from the Yazidi community, a mostly Iraq-based Kurdish-speaking religious minority that ISIS considers heretics.

But Afrin said the victims had not yet been identified.

"The women are believed to be Yazidi women captured by the group as sabaya (sex slaves), the fate of many of whom is still unknown," Dudeki said.

ISIS massacred hundreds of Yazidi men when they seized swathes of northern Iraq in 2014, enslaving thousands of women and girls.

Since the start of this year, 45 Yazidi women and children kidnapped by ISIS in Syria have been freed, the Office for Yazidi Abductees' Affairs said Thursday.

Of those, 14 were freed this week alone, office chief in Duhok Hussein al-Qaidi said in a statement.

"During the past 48 hours, we have freed 14 Yazidi children between the ages of five and 16 from ISIS in Syria," he said Thursday.

"Our efforts to free the abductees and bring them back to their families as soon as possible will continue," he added.

Earlier in February, the Kurdish authorities in north-eastern Syria discovered a mass grave near the city of al-Raqa, holding an estimated 3,500 bodies -- the largest to date.

Dozens of mass graves containing the bodies of civilians and fighters killed by ISIS had been discovered across Syria and Iraq in recent years.