William Roebuck, the deputy Special Envoy to the Global Coalition to Defeat ISIS, said Turkish-backed rebels committed war crimes and ethnic cleansing during Turkey's military operation in northeast Syria, the New York Times reported on Thursday.

“Turkey’s military operation in northern Syria, spearheaded by armed Islamist groups on its payroll, represents an intentioned-laced effort at ethnic cleansing," Roebuck said in an internal memo, calling the abuses “what can only be described as war crimes and ethnic cleansing.”

Roebuck said some 200 civilians were killed and over 100,000 people were forced to flee due to Turkish incursion.

The offensive has brought accusations against the Turkish government of genocide, ethnic cleansing, and support for terrorism. Several major news outlets raised fears of genocide in northern Syria since the day the operation was launched, and a U.S. senator took up the case in Congress using the same term.

The Turkish-backed rebels spearheading the country’s offensive in northeast Syria were accused of committing war crimes, and U.S. officials received evidence regarding the issue, according to Washington’s Syria envoy James Jeffrey.

Roebuck also asked whether tougher diplomacy, more serious threats of economic sanctions and increased military patrols could have prevented Turkey from invading the region, according to NYT.

“It’s a tough call, and the answer is probably not,” Roebuck said. “But we won’t know because we didn’t try.”

Turkey had long threatened with launching a military offensive in northeast Syria, targetting Syrian Kurdish forces which have been a key partner in the fight against the Islamic State.

Three days after U.S. President Donald Trump's decision to withdraw troops from the region, Turkey launched an offensive. Trump's withdrawal policy appeared to many a green light for Turkish incursion into the region.