Turkey's president has announced the country is conducting a "serious" operation against extremist groups in Syria's northwestern Idlib province with Turkey-backed rebels.

President Recep Tayyip Erdogan said Saturday the operation was a "new step" to establish security in Idlib. He says: "Today, there is a serious operation in Idlib and it will continue."

Erdogan spoke at his political party's conference in Afyonkarahisar province in western Turkey.

Responding to journalists' questions after the televised speech, Erdogan said Turkish soldiers were not yet in Idlib and the military was supporting opposition Free Syrian Army forces from within Turkey's borders.

The rebels are fighting the al-Qaida-linked Levant Liberation Committee, formerly known as Nusra Front.

Erdogan said Turkey would not desert civilians in Idlib and would not allow a "terror corridor" in northern Syria.