"Our mission is to prevent the creation of a terror corridor across our southern border, and to bring peace to the area", Erdogan added.
Turkey views Kurdish YPG fighters in northeast Syria as terrorists due to their ties to militants waging an insurgency inside Turkey, an influx of non-Kurdish Syrians would help it secure a buffer against its main security threat.
This is a breaking news story and will be updated.
He had said earlier this week that he was working on a bipartisan bill to sanction Turkey if they invade Syria.
In the meantime, Syrian Democratic Forces, which have vowed to defend itself against any perceived Turkish incursion called on the US-led coalition and the global community to implement a no-fly zone over northern Syria similar to the one implemented in Iraq.
But Kurdish officials have warned that they would have to divert their forces away from guarding IS prisoners in case of a Turkish assault.
In more than 30 years of its terrorist campaign against Turkey, the PKK - which is listed as a terrorist organisation by Turkey, the United States and the European Union - has been responsible for the deaths of 40,000 people, including women, children and infants, Anadolu pointed out. "We call upon our people, of all ethnic groups, to move toward areas close to the border with Turkey to carry out acts of resistance during this sensitive historical time", it said.More news: A new Google Assistant voice is here: Actress Issa Rae
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Turkish aircraft and artillery began striking positions in Syria immediately after Erdogan's announcement, according to media reports.
Turkey says it is ready to clear Kurdish fighters from the Syrian border.
Another Turkish official denied that the country had begun its operation against the Kurdish fighters.
The statement said the mobilization would last for three days.
Turkey's Minister of National Defense, Hulusi Akar, tweeted that the United States, United Nations and North Atlantic Treaty Organisation, among others, had been informed of the operation at 7 a.m. ET. It went on to call on the global community and those countries fighting against ISIS "to carry out their responsibilities" to avoid a "possible impending humanitarian disaster".
The preparation for the operation was announced as the surprise decision to withdraw U.S. troops cleared the path for the Turkish operation.
Graham warned that Trump's decision to withdraw the troops opened the way for a Turkish strike on Kurdish-led forces long allied with Washington.
He said, "if Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey".
In the build-up to the anticipated offensive, Syria had said it was determined to confront any Turkish aggression by all legitimate means.
Fighters from Turkish-backed Syrian rebel groups were also preparing to take part in the Turkish operation in northern Syria.