BEIRUT (Reuters) - The U.S.-led coalition carried out an early-morning helicopter landing operation in a part of northern Syria held by Turkish-backed rebels, a spokesperson for the rebel group told Reuters in what he said was the first raid of its kind in the area.

       The U.S.-led coalition, formed to fight the Islamic State group in Iraq and Syria (ISIS), could not immediately be reached for comment.

       "Till now the circumstances are unclear," a spokesman for the Turkey-backed Syrian National Army (SNA) Major Youssef Hamoud told Reuters.

       He said the operation, which has since ended, took place near the village of Al-Humaira, just a few kilometres from the Turkish border, and that U.S.-made Chinook and Black Hawk helicopters were involved.

       "This is the first (U.S.) helicopter landing operation to happen" in areas under the SNA's control, he said.

       The SNA includes groups that fought against Syrian government forces during the country's 11-year civil war. It is a rival of other armed groups such as ISIS and Al Qaeda-backed jihadists.

       A source in touch with rebels in the area said clashes erupted during the operation.

       U.S.-led forces have in the past carried out helicopter landing operations and drone strikes in areas of northern Syria controlled by U.S.-backed Kurdish forces and to the west in Idlib where jihadist rebels formerly linked to Al Qaeda hold sway.

       United States special forces in February undertook a helicopter landing operation to the west in Syria's Idlib province controlled by jihadist Hayat Tahrir al-Sham (HTS) that led to the death of ISIS leader Abu Ibrahim Al-Hashemi Al-Quraishi.

       (Reporting by Suleiman al-Khalidi; Writing by Timour Azhari; Editing by Lincoln Feast)