Palestinian security arrested seven Iranian citizens during a raid at the Islamic University, a Hamas stronghold in Gaza City, a security official said, and another committed suicide during the raid.
The arrest came during a large-scale assault by Fatah-affiliated gunmen on the university. The security official spoke on condition of anonymity because of the sensitivity of the issue.
A Hamas official denied the claim and said there were no Iranian citizens at the university.
The raid came at the end of a day of clashes that collapsed a three-day truce between the warring factions.
Iran has supplied Hamas with funds, but there have been no previous claims of Iranians working with Hamas in Gaza.