Syrian Democratic Forces (SDF) spokesman Talal Ali Sello, pictured here in 2015, is "in the hands of" the Turkish intelligence after handing himself over to pro-Ankara forces, a Turkish daily reported on November 17, 2017

A spokesman for the US-backed Syrian Democratic Forces (SDF) fighting Islamic State extremists is "in the hands of" the Turkish intelligence after handing himself over to pro-Ankara forces, a Turkish daily reported Friday.

Talal Sello "gave himself up" to Syrian opposition fighters -- which Turkey calls the Free Syrian Army (FSA) -- on Wednesday, according to Turkish reports.

Sello was then taken to the southern Turkish province of Gaziantep bordering Syria, the Hurriyet newspaper said, adding that he was "giving answers to questions" from the Turkish National Intelligence Organisation (MIT) about the activities of the Syrian Kurdish militia.

The fate of the burly Sello -- who became a prominent face due to his media updates during the SDF's fight with jihadists for Raqa -- has been shrouded in mystery since it emerged this week that he had left the force.

Mohammad al-Abdallah, of the Syrian rebel group Forqat al-Hamz, speaking to AFP in Beirut, described Sello's move as a "defection".

But the SDF denied he had defected, saying it believed Sello was taken "as a result of a special operation by Turkish intelligence."

The SDF added that Sello "received threats against his children who are in Turkey."

The SDF includes Arab forces but is dominated by Syrian Kurdish fighters from the Peoples' Protection Units (YPG). Sello is of Turkmen origin.

Ankara views the YPG as a terror group linked to the outlawed Kurdistan Workers' Party (PKK) which has been waging an insurgency inside Turkey since 1984. It has dismissed the SDF has merely a front for the YPG.

The PKK is blacklisted as a "terrorist" organisation by Ankara, the United States and the European Union.

While Washington views the YPG as the most effective fighting force on the ground against Islamic State jihadists in Syria, Ankara has railed against the American support.

The Kurdish-led force expelled IS from its de facto capital Raqa in northern Syria last month, one of a series of defeats against the group.

Turkey has cautioned against the creation of a "terror corridor" in northern Syria and had repeatedly warned it could launch an operation against the militia in the YPG-controlled town of Afrin.

Turkish President Recep Tayyip Erdogan said on Friday that Afrin "needs to be cleared of the YPG terror group."

According to Hurriyet, Sello answered questions from Turkish officials about the "activities of the YPG, its structure and the situation in Afrin".

Crucially, he was also asked about what kind of preparations the YPG was making in the event of an attack by the Turkish military on Afrin, the daily added.

The UK-based Syrian Observatory for Human Rights (SOHR) confirmed that Sello was in the hands of Turkish intelligence and said he had been "brought to Turkey by trickery."