The operation has been highly expected in the province, where al-Qaida-linked fighters enjoy wide influence, after last month's talks in the Kazakh capital of Astana during which Turkey, Iran and Russia agreed on setting up "a de- escalation zone" in the province.
Turkey is a strong backer of Syrian opposition fighters while Iran and Russia back President Bashar Assad. Moscow joined the war two years ago siding with Assad while Tehran has sent thousands of Iran-backed fighters tipping the balance of power in the president's favour.
Erdogan said the operation was a "new step" to establish security in Idlib, promising Turkey would not desert civilians there.
"Today, there is a serious operation in Idlib and it will continue," he said at his political party's conference in Afyonkarahisar province in western Turkey.
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Responding to journalists' questions after the televised speech, Erdogan said: "The Free Syrian Army is leading an operation in Idlib right now," referring to moderate rebel groups in Syria. He added that the Turkish military was not yet in the province.
A Syrian rebel commander speaking from Turkey said no military operations are ongoing at the moment but said preparations were underway for Turkish troops and FSA fighters to enter Idlib.
"The aim of the operation is to implement the Astana agreement by setting up Turkish observation posts similar to those of Russia," Lt. Col. Fares al-Bayoush said in an exchange of text messages.
"This cannot be achieved without confronting the Nusra Front," he said. "The aim is to finish Nusra Front."
Last month, a negotiated "de-escalation zone" in the mostly rebel-held province of Idlib was announced during talks in Astana, the capital of Kazakhstan. Iran, Turkey and Russia reached the deal for four de-escalation zones earlier this year as part of their efforts to negotiate an end to the Syrian civil war.
Turkey's official Anadolu news agency reported that the Turkish "deployment" would be to reach de-escalation goals rather than engage in clashes with local militia or the Syrian army.
The Turkish president warned the country would not permit a "terror corridor" along its border, referring to extremists groups as well as U.S.-backed Syrian Kurdish militants.