A Muslim cemetery in Kifl Harith, northwest of Ariel, was vandalized early Friday morning by Jews who had come to pray at the nearby grave of biblical leader Joshua (Yehoshua Bin-Nun).
The vandals spray-painted "Death to Arabs" on some graves and broke others. A total of nine tombstones were desecrated.
According to the IDF, the vandals were among some 1,300 worshippers who had come to pray at the grave.
Most, the army said, behaved in a manner "appropriate to a holy place." "A small group decided to cause a provocation," an IDF officer told Army Radio.
The military informed organizers of the early-morning prayers of the incident and received assurances that the damage would be repaired this week.
Rabbis for Human Rights and the Anti-Defamation League both condemned the attack.
"We deplore this act of violent intolerance on Islamic sites just as we are horrified by attacks on Jewish cemeteries and holy places," the ADL said in a statement released on Friday.