A new report from human rights group Amnesty International suggests that Kurdish forces in northern Syria, among the most significant U.S. ground partners in the fight against the Islamic State, may have committed war crimes with a campaign of displacement and home demolitions aimed mostly at the local Arab population.

In the report released on Monday, Amnesty says it has found evidence that the local armed group known as the People’s Protection Units – better known by the acronym “YPG" – forced Arabs and Turkmen in northern Syria from their homes on behalf of the Democratic Union Party (PYD), a Kurdish political organization that has held de facto control of northern Syria's so-called "Autonomous Administration" since January 2014.

“By deliberately demolishing civilian homes, in some cases razing and burning entire villages, displacing their inhabitants with no justifiable military grounds, the Autonomous Administration is abusing its authority and brazenly flouting international humanitarian law, in attacks that amount to war crimes,” Lama Fakih, a senior crisis adviser at Amnesty, said in a statement.

The YPG has earned praise for its fight against the Islamic State and the United States has offered a variety of support for the Kurdish group during the conflict, including airstrikes, training and supplies. On Monday, the YPG announced it would be joining forces with Syrian Arab groups under the name "the Democratic Forces of Syria." The move prompted speculation that Kurdish forces would be involved in a new U.S. strategy designed to push into Raqqa, the Islamic State’s base of operation.

Amnesty's report suggests that sometimes entire communities have been displaced by Kurdish forces in what it says may have been retaliation for perceived support or links to the Islamic State or other groups. While Kurdish authorities have argued that cases of displacement were limited and had occurred only for security reasons, Amnesty say that they have been able to find examples where local populations had not only been displaced, but their homes had been destroyed.

For example, satellite images obtained by Amnesty appear to show 225 buildings standing in the villages of Husseiniya near Tel Hamees in June 2014. However, satellite images of the same area appeared to show only 14 buildings remaining a year later. Locals say that their homes had been demolished after the YPG took the village from Islamic State control. "The destruction reflected in the satellite imagery is not consistent with shelling but rather the demolition of the village," Amnesty's report reads.

Another witness account said that in one situation Kurdish forces had poured gasoline on a house and threatened to set it alight while inhabitants were still inside. A different witness told Amnesty that YPG fighters told residents they would be hit with U.S. coalition airstrikes unless they left their homes. “They told us we had to leave or they would tell the U.S. coalition that we were terrorists and their planes would hit us and our families,” a witness told Amnesty.

Amnesty has called for a stop to the displacement and demolitions and said that all civilians whose homes were destroyed should be compensated. U.S. officials were not able to provide immediate comment.

U.S. cooperation with Kurdish forces has proven controversial during the Syrian conflict. Turkey, a key regional ally, considers the YPG and PYD terrorist organizations for their link to the Kurdistan Workers Party, or PKK, a Kurdish separatist group that has long fought the Turkish state. While the United States considers the PKK a terrorist organization, it has not applied the same label to the YPG and PYD.

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