The UN refugee agency says it has received reports that the Islamic State group may have captured up to 3,000 Iraqis who were fleeing violence and that 12 of them may have been killed.

In a report published Thursday, the U.N. High Commissioner for Refugees said the internally displaced people from villages in Hawiga district had been trying to flee to the northern Iraqi city of Kirkuk when they were captured by IS.

A spokesperson for the Geneva-based UNHCR couldn’t immediately be reached Friday for more information or to provide details about the sourcing of the reports.