The mass killings of Sunni tribesmen battling the Islamic State have added urgency to Iraqi government efforts to support pockets of resistance against the militants. But distrust, a lack of financing and corruption threaten the process, tribesmen and officials say.

In a flurry of meetings in recent weeks, tribal leaders have demanded that Prime Minister Haider al-Abadi address problems of missing weapons and lack of support as they hold out against extremists in the face of mass detentions and executions. Hundreds of tribesmen have been summarily executed in the western province of Anbar over the past month, with hundreds more rounded up north of Baghdad.

The slayings have underscored the predicament of Sunni tribes that have resisted Islamic State extremists, often with little help from the central government. The killings threaten to undermine the government strategy of mobilizing the Sunni tribes against the Islamic State in the tribes’ areas — a key pillar in efforts to crush the militants. […]