Turkish-backed forces are deliberately releasing detainees affiliated with IS from unguarded prison camps in northern Syria, according to several US officials.
The claims, reported by Foreign Policy on Monday, directly counter the narrative from US President Donald Trump that the Kurds have been releasing IS prisoners to "get the US involved" in the fighting.
After the US abruptly departed northern Syria last week, Turkey launched a massive bombardment on rival Kurdish forces across the border.
In the fighting, there has been a flurry of claims about what is happening to the scores of IS prisoners who were under Kurdish guard, as hundreds have already escaped.
And, according to Foreign Policy, it is "Ankara's radical proxies" who are freeing individuals affiliated with IS.
US officials quoted in the article point the finger at the Free Syrian Army, also known as the Turkey-supported opposition (TSO), a group of Syrian rebels with links to extremist groups.
"The TSO is deliberately releasing Islamic State detainees previously held by the Kurdish fighters," US officials are quoted as saying
Foreign Policy quoted one "senior US administration official" who said "the US has evidence that the prisons the [Kurdish-led] SDF said they could no longer guard because they were seized by Turkish-backed forces are the same ones where the prisoners are being released".
The officials also told the outlet that Free Syrian Army forces "even deliberately targeted US troops in Kobani on Friday".
Mr Trump has faced criticism for echoing Turkish claims that the Kurds had been releasing prisoners.
"Kurds may be releasing some to get us involved," he tweeted.
While a senior Turkish government official told reporters, "there is only one [IS] prison in our [operation] region and we have seen it was emptied by the YPG," referring to the Kurdish People's Protection Units militia.
Ankara says the YPG is a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK), which has waged a bloody insurgency inside Turkey since 1984.
According to the Syrian Observatory for Human Rights, a Britain-based war monitor, the Turkish attack has already left 133 pro-Kurdish fighters and 69 civilians dead.
The United Nations believes about 160,000 people have been displaced.
Additional reporting: AFP
