After days of clashes with Islamist opposition groups, Syrian Kurds seized control of the border town of Ras al-Ain Thursday.
With only a razor wire fence separating the town from Turkey, Turkish troops fired over the frontier after rocket-propelled grenades and bullets landed on their territory, killing two Turkish citizens.
"Turkey is taking and will continue to take every precautionary step that is necessary to protect its citizens and its territory," said Ankara's Foreign Minister Ahmet Davutoglu in a statement Friday.
The Kurdish fighters belong to the PYD party, which Turkey calls a "separatist terrorist organization."
According to Robert Lowe of the Middle East Centre at the London School of Economics, Ankara fears PYD’s growing strength in Syria.
"They’ve always been hostile to the Kurdish population in Syria gaining or improving its position in that country," he said. "So they’re looking on with some concern, if not hostility, especially as the major Kurdish group in Syria is closely aligned to the PKK in Turkey, the largest, most powerful and armed force."
The fall of Ras al-Ain comes at a sensitive time as Ankara holds peace talks with the Kurdistan Workers’ Party (PKK), says Fadi Hakura of policy institute Chatham House.
“Already the PKK issued what they called a final warning to Prime Minister Erdogan of Turkey to take some concrete steps forward in the peace process or otherwise the engagement will grind to a halt," he said.
With bigger battles to fight elsewhere, Syrian government forces have given the Kurds a large degree of autonomy, but they are now being drawn in to battles over territory, says Lowe.
“There’s competition for control of those border crossings to Turkey and the access into Syria," he said. "There’s competition for control of some oilfields where some Kurds live in large numbers, and this is strongly opposed by Islamists.”
Opposition Kurdish groups claim Turkey is aiding Islamist groups in Syria such as the al-Qaeda-linked Nusra Front, Hakura says that Ankara denies the charge.
“Many of the Islamist-based fighters in Syria happen to be in northern Syria," he said. "The only way that such Islamist fighters could enter into Syria is via the Turkish-Syria border."
Lowe says there will likely be more Islamist-Kurdish battles like that for Ras al-Ain.
"It’s possible for groups who have weapons to simply try and take control of a border post or of the smuggling networks to try and gain power and resources," he said. "So I fear that we’ll see an increase in these clashes."
Turkey has called on the United Nations to take action after violence spilled over its borders, saying the time for the Security Council to do its job is now.