Two mass graves, containing a total of nearly 140 corpses of members of the minority Yazidi community, were discovered over the weekend in the northern Iraqi town of Sinjar, according to media reports. The corpses were discovered by Kurdish forces that are consolidating their gains in the region after retaking the town from the Islamic State group, also known as ISIS.

“I expect that about 15 to 20 more graves will be discovered,” Qasim Simo, the head of security in Sinjar, reportedly said. “Killing these innocent people is one of the crimes [ISIS] perpetrated against the Yazidi Kurds.”

Kurdish Peshmerga fighters, speaking to Al Jazeera, said that they dug up bones, clumps of hair and personal items such as shoes, jewelry and walking sticks from the grave.

“We keep finding evidence of their actions, and this needs to be documented and recorded,” Simo told Al Jazeera.

Last year, after ISIS overran Sinjar, thousands of Yazidis -- who practice an ancient religion predating Islam and Christianity, and are considered “devil worshippers” by the Sunni militant group -- were killed, raped and enslaved. Last week, Kurdish forces -- backed by U.S.-led airstrikes -- pushed the extremist group out of the town after a two-day offensive. 

While most of the surviving Yazidi population now lives in makeshift camps in the Kurdistan region, an unknown number of Yazidi women are still being held captive by ISIS.

“We understand this is war. We know people will die. But this is more. We will never forget what they did here, and we will have our revenge,” Naib Jassim, a Yazidi who said his family members were among those buried in the mass grave, told Al Jazeera.