MAZAR-I-SHARIF, Afghanistan (Reuters) - Afghan police have discovered mass grave containing the bodies of at least 36 victims of a recent militant attack on a village, officials said on Wednesday.

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One grave in the northern province of Sar-e Pul held 28 bodies and another contained eight, said provincial government spokesman Zabihullah Amani.

“Most of the victims were beheaded,” he said, noting that all were men, except for three boys between the ages of eight and 15.

A third mass grave had been located but it was in an area under Taliban control, and security forces were searching for more possible graves, Amani added.

On Wednesday, residents held funerals for several victims of the raid.

At least 62 people have been confirmed dead in the attack on Mirza Olang village last week, with the number expected to rise, according to the Sar-e Pul governor’s office.

The Afghanistan Independent Human Rights Commission said a preliminary investigation suggested that militants from the Taliban and Islamic State, who are normally bitter rivals, acted together.

That has been denied by the Taliban, who said they had carried out the attack alone and did not kill any civilians.

Islamic State issued a statement on Monday claiming it had led the attack and killed about 54 Shi’ite Muslims, a minority group in Afghanistan that has often come under attack from Islamic State.

Villagers who escaped from Mirza Olang told reporters they saw fighters carrying both the white banner of the Taliban and the black banner of Islamic State.

In a region where bands of fighters often switch between different militant groups, it can be difficult to establish allegiances with any certainty.