Syria's Kurdish People's Protection Units (YPG) denounced rights group Amnesty International for accusing its fighters of war crimes by forcibly displacing people and demolishing homes.
Amnesty said this week that Syrian Kurdish forces had carried out a "campaign of collective punishment" against villages previously held by the Islamic State group.
It accused them of preventing people from returning to their villages after IS was expelled and, in some cases, destroying houses belonging to residents accused of IS sympathies.
The YPG rejected the allegations and said the report would cause tensions between Arabs and Kurds in Syria.
"The Amnesty International report is arbitrary, biased and unprofessional," the YPG said, also calling it "dangerous, unethical and unworthy of" the organisation.
"This report will contribute greatly to the deepening of ethnic tensions and portrays things as a sectarian war between Kurds and Arabs," the statement added.
Its response includes line-by-line rebuttals of allegations including the deliberate destruction of homes and the razing of one village in northeast Syria.
The Kurdish force said Amnesty had failed to take into consideration the damage caused by years of fighting and an IS strategy of using mines and other explosives.
"Successive terrorist organisations in the region pursued a war strategy of planting improvised explosive devices and mines, using car and suicide bombs and booby-trapping houses," the YPG said.
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"The authors of the report ignore what Daesh (IS) terrorists and others before them in the region did during their defeats in terms of demolition, burning and destruction."
The group also pointed to its alliance with Arab fighters, which it said "removed all doubt" that it would engage in the forced displacement of any particular ethnic group.
But Amnesty's report said the destruction it examined on a fact-finding mission to 14 towns and villages did not result from fighting.
It quoted villagers who said Kurdish forces had deliberately razed the village of Husseiniya in Hasakeh province.
Amnesty said satellite images showed that nearly 94 percent of the village had been destroyed between June 2014 and June 2015.
The YPG cast doubt Amnesty's witnesses, saying the group had interviewed people "who fled the area with Daesh and are stained with the blood of the Syrian people."
Syria's Kurds have proved to be the country's most effective force against IS, but their advances with the help of a US-led coalition's airpower have at times exacerbated existing ethnic tensions in northeastern Syria.
The YPG has sought to fight allegations of abuses against non-Kurds, pointing to its alliances with other forces.
This week it announced a formal coalition with Arab and Syriac Christian fighters in northern Syria.