Turkey said eight of its troops were killed on Saturday in Ankara's military operation against a Syrian Kurdish militia, the deadliest day in the two-week-old offensive in the enclave of Afrin.
In a statement late on Saturday, the Turkish military said five soldiers were killed after their tank in Syria came under attack near Afrin. The soldiers could not be saved despite all attempts, it said.
Earlier in the day, three Turkish soldiers were reported killed in the Afrin offensive — one was killed in the area of the tank attack, another in northern Syria and the third on the Turkish side of the border, in what Ankara said was an attack by Syrian Kurdish militiamen.
The total death toll for Turkish troops since the operation, code named Olive Branch, started on January 20 now stands at 13.
Turkey launched the incursion into Afrin to rout the US-backed Syrian Kurdish militia, known as the People's Protection Units or YPG, which it considers to be a terrorist organisation and an extension of Kurdish insurgents fighting within Turkey.
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From Istanbul, Turkish presidential spokesman, Ibrahim Kalin, said Turkey will not tolerate the presence of the YPG "anywhere" along its southern border, hinting that Ankara might expand the Afrin operation eastward. Turkey's first demand is to see the YPG move east of the Euphrates River and leave the town of Manbij, where American troops backing the Syrian Kurdish fighters are stationed, Mr Kalin said.
He called on the United States to "disengage" from the YPG and said Turkey will continue communications with "our American allies to avoid any confrontation".
Turkey shares a 911-kilometre border with Syria. The YPG controls much of the territory along the border and an uninterrupted strip from Manbij to the Iraqi border.
Also on Saturday, Syria's Foreign Ministry has dismissed as "null and void" US accusations that Bashar Al Assad's government is producing and using "new kinds of weapons" to deliver deadly chemicals despite committing to abolish its program in 2013.
The American statements are "nothing more than lies" based on accounts of what the Trump administration called its partners on ground, the ministry said. It also said reports by Western-backed media outlets about Damascus using chemical weapons were "a new version of US and Western desperate intentions to create" an excuses to attack Syria.
US President Donald Trump has not ruled out additional military action to deter attacks or punish Mr Assad, administration officials said earlier this week, although they did not suggest any action was imminent.