ISTANBUL- There has been some withdrawal of militants from the demilitarisation zone in Idlib following the Russia-Turkey deal on the northwestern Syrian region, the U.S. special representative for Syria engagement told reporters in Ankara.

The two countries reached a deal to set up a buffer zone running 15-20 km (9-13 miles) deep into rebel territory and evacuated of all heavy weapons and all jihadists by Monday. Hayat Tahrir al-Sham (HTS), a jihadist alliance spearheaded by al-Qaeda's former Syrian affiliate, is the most powerful jihaidst alliance in Idlib.

"The withdrawal of heavy weapons is complete by all accounts," James Jeffrey said. "There is some question as to whether everybody from (Hayat Tahrir al-Sham) has left."

(Writing by Sarah Dadouch; Editing by David Dolan) ((Sarah.Dadouch@thomsonreuters.com;))