Forces entered the country’s Afrin province today just 24 hours after pounding the region with airstrikes.
Turkish Prime Minister Binali Yildirim reportedly said they are targeting US-backed Kurdish fighters.
Shocking pictures show dozens of tanks and armoured vehicles crossing over the border in a terrifying display of military might.
But the Syrian-Kurdish YPG militia has denied there is a full-scale invasion underway, claiming forces clashed in Afrin but Turkish soldiers were beaten back.
YPG official, Nouri Mahmoudi, said “all the Turkish military’s ground attacks against Afrin have been repelled so far and they have been forced to retreat.”
A statement from the militia said: “Our people are holding on to their land and do not accept surrender… we repeat our determination to protect our people in Afrin against the attacks.”
Turkey has claimed the massive movement of military hardware into the country is simply to create a 30km-deep “safe zone” in the north of the country.
But the YPG – which is backed by the United States but classed as a terrorist organisation by Turkey – said they had killed six civilians and three of its fighters.
Turkey has dubbed the action “Operation Olive Branch”, which has seen them carry out relentless airstrikes yesterday.
Turkish President Tayyip Erdogan’s spokesman, Ibrahim Kalin, wrote on Twitter: “In its second day, OliveBranchOperation continues to ensure peace and security for our people, protect Syria’s territorial integrity and eliminate all terrorist elements in the region.
“Turkey expects its allies to support its fight against terrorism in all of its forms.”
Turkey’s state-run Anadolu news agency reported that four rockets fired from Syria hit the border town of Kilis overnight, damaging houses. Turkish security forces then retaliated, it said.
The operation pits Turkey against Kurdish fighters allied to the US at a time when ties between Ankara and Washington – NATO allies and members of the coalition against ISIS – reach breaking point.
Turkey sees the YPG as an extension of the outlawed Kurdistan Workers Party (PKK), which has carried out a deadly, three-decade insurgency in Turkey’s mainly Kurdish southeast.
But the US is backing the YPG in Syria, seeing it as an effective partner in the fight against ISIS.