Turkey has sent more tanks into northern Syria and demanded Kurdish militia fighters retreat within a week as it seeks to secure the border region and drive back Islamic State with its first major incursion into its neighbour.
Turkish special forces, tanks and warplanes on Wednesday entered Jarablus, one of Islamic State's last strongholds on the Turkish-Syrian border, in a US-backed offensive. Gunfire and explosions echoed around hills in the region on Thursday.
President Tayyip Erdogan and senior government officials have made clear the aim of Operation Euphrates Shield is as much about stopping the Kurdish YPG militia seizing territory and filling the void left by Islamic State as about eliminating the radical Islamist group itself.
Turkey, which has NATO's second biggest armed forces, demanded that the YPG retreat to the east side of the Euphrates river within a week. The Kurdish militia had moved west of the river earlier this month as part of a US-backed operation, now completed, to capture the city of Manbij from Islamic State.
Ankara views the YPG as a threat because of its close links to Kurdish militants waging a three-decade-old insurgency on its own soil. It has been alarmed by the YPG's gains in northern Syria since the start of the Syrian civil war in 2011, fearing it could extend Kurdish control along Turkish borders and fuel the ambitions of its own Kurdish insurgents.
Turkey's stance has put it at odds with Washington, which sees the YPG as an ally against Islamic State. It is one of the most powerful militias in Syria and regarded as the backbone of the Syrian Democratic Forces (SDF), a US-backed alliance formed last October to fight the jihadist group.
Defence Minister Fikri Isik said preventing the Kurdish PYD party - the political arm of the YPG - from uniting Kurdish cantons east of Jarablus with those further west was a priority.
"Islamic State should be completely cleansed, this is an absolute must. But it's not enough for us ... The PYD and the YPG militia should not replace Islamic State there," Isik told Turkish broadcaster NTV.
"The PYD's biggest dream is to unify the western and eastern cantons. We cannot let this happen," he said.
US Secretary of State John Kerry told Turkish Foreign Minister Mevlut Cavusoglu by phone on Thursday that YPG fighters were retreating to the east side of the Euphrates, as Turkey has demanded, foreign ministry sources in Ankara said.
A spokesman for the US-led coalition against IS also said the SDF had withdrawn across the Euphrates, but had done so "to prepare for the eventual liberation" of Raqqa, the radical group's stronghold in northern Syria.
Isik said the retreat was not yet complete and Washington had given assurances that this would happen in the next week.
"We are closely following this ... If the PYD does not retreat to east of the Euphrates, we have the right to do everything about it," he said.
