"We will not allow a terrorist corridor to be established on our border", Erdogan said in his address.
"There is a serious operation in Syria's Idlib today, and this will continue", Erdogan told members of his AK Party in a speech.
Turkish forces exchanged fire on Sunday with jihadists from Al-Qaeda's former Syrian affiliate on the border of Idlib province, a monitor and eyewitnesses said, a day after Ankara announced an imminent operation there.
The Turkish president said the major offensive was the follow-up of the so-called Euphrates Shield Operation in northern Syria, which was launched in August a year ago without granting any permission from Damascus, in a declared objective of clearing Turkey's southern border of the Takfiri Daesh terrorist group.
The factions included in the Euphrates Shield operation, which are based in different areas in northern Syria, have upped readiness to the maximum over the past three days in anticipation of the entry to Idlib, where Hay'at Tahrir al-Sham (HTS), which includes the al-Qaida-linked Nusra Front, is in control of much of Idlib, he added.
It is not clear what role the Turkish military will play in the operation. "If you make a step toward us, we will make two toward you", Cavusoglu said.
Danish divers find journalist's body parts
They did not determine a cause of death at the time but found it had been "deliberately mutilated" and suffered 14 stab wounds. The findings were made about a kilometer from where her torso was found on August 21 after it washed ashore in Copenhagen .
He also claimed Turkey would be prepared to work with Green politician Cem Ozdemir, who is of Turkish origin and a fierce critic of Turkish President Recep Tayyip Erdogan.
State-run Anadolu news agency said there was a major build up of commando units and military vehicles around the town of Reyhanli bordering Idlib close to the Cilvegozu border crossing.
Fighting broke out on the border of Turkey and the Syrian province of Idlib on Sunday ahead of a Turkish advance into the region.
Ankara has been expected to take up the supervision of a ceasefire in Idlib province, as part of the Turkish-Iranian-Russian sponsored de-escalation programme in Syria.
German Chancellor Angela Merkel came under enormous pressure from her rivals to sharpen tone towards Turkey, particularly due to the arrests of around 10 German citizens, including a reporter and a human rights activist, for alleged support for terrorist organisations. "It is a very risky area - Turkey may face a backlash from moderate rebels if it can't deliver humanitarian services" and may also "come under pressure" from Russian Federation and Iran to eliminate militants, he said.
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