The State Department remains concerned by credible reports of human rights abuses committed by Turkish-backed fighters in parts of northeast Syria seized during military operations against US-allied Kurdish fighters, according to a new inspector general's report.

The State Department has received reports of “arbitrary detentions, extrajudicial killings, seizure of and resettlement of new populations in private properties, the repeated and deliberate shutting off of water access to half a million civilians, and transfer of arbitrarily-detained Syrians across an international border into Turkey,” according to the Lead Inspector General report on Operation Inherent Resolve, the operational name for the US fight against the Islamic State in Iraq and Syria. The report released Tuesday covers the period of April 1 to June 30.

“We have reiterated our expectation that Turkey, and the Syrian opposition, investigate alleged violations and abuses and promote accountability where appropriate,” the State Department said.

The State Department told investigators it had no evidence that the Syrian Interim Government, a political body that operates in Turkish-controlled areas of northern Syria, "has consistently arrested, prosecuted, or otherwise held accountable any [Turkish-supported opposition group] members implicated in human rights abuses or violations of the law of armed conflict."