Syrian rebels supported by Turkey and US-backed Syrian Kurdish forces clashed Thursday in the north of the country, activists and Kurdish officials said, raising fears of a new confrontation over territory amid a Turkish led intervention.
Kurdish officials described the incidents as skirmishes which took place near Ain al-Bayda, just south of Jarabulus, a border town in northern Syria which the rebels wrested from Islamic State control on Wednesday.
Turkey launched its first major land offensive inside Syria on Wednesday, with tanks backed by airstrikes taking part in an operation to capture Jarabulus alongside more than 1,000 Syrian opposition fighters, according to rebels.
Turkish President Recep Tayyip Erdogan said on Wednesday that the operations were targetting both Islamic State and the Syrian Kurdish Democratic Union Party (PYD) whose armed wing has been the key US ally on the ground against the jihadists.
The PYD's militia, the People's Protection Units (YPG), meanwhile said it had handed over the key city of Minbij, south of Jarabulus, to local civil and military councils set up by its allies, apparently in line with what the Turkish government is demanding.
Kurdish forces captured Minbij in mid-August after a gruelling ten-week campaign backed by US airstrikes. The group said more than 260 of its members and allies were killed by Islamic State.
Their move was intended to cut Islamic State off from its last access to the Turkish border in the Jarabulus region, and make it harder for it to bring supplies and fighters to its de facto Syrian capital of al-Raqqa and the rest of its territories in Syria and Iraq.
However, it raised fears in Ankara and among the Syrian opposition of Kurdish expansionism, in particular that the Kurds might seek to strike further west and link up Minbij with their enclave of Efrin in north-west Syria.
Ankara is particularly concerned about Kurdish advances because they view the PYD and YPG as the Syrian branch of the Kurdistan Workers Party (PKK) which is fighting an insurgency inside Turkey.
US Vice President Joe Biden said this week that the Kurds must retreat eastwards, over the Euphrates River. Biden said the US would otherwise cut off support.
"The whole zone, including Jarabulus, needs to be cleared of the PYD," Turkish Prime Minister Binali Yildirim said, referring to the wider Minbij area.
The spokesman for the US-led anti-Islamic State coalition said that most contingents of the Syrian Democratic Forces, an alliance dominated by the YPG, have moved back east across the Euphrates River, to the east. Some remained for mine clearing operations.
"The Syrian Democratic Forces have moved east across the Euphrates to prepare for the eventual liberation of Raqqa, Syria," spokesman Colonel John Dorrian wrote on his Twitter feed. Raqqa is the Islamic State's de-facto capital in Syria.
In Jarabulus, the victorious Syrian rebels - who appear to have captured the town without much resistance from Islamic State - said that they had also taken control of several villages on the border which had been held by the jihadists.
Rami Abdulrahman, the head of the Syrian Observatory for Human Rights, a watchdog, said it was abnormal for Islamic State to withdraw without a fight. He said their fighters simply "left the area."
Turkey, a staunch backer of various Syrian rebel factions, appears keen to set up a buffer zone in northern Syria.
Turkish media reported that Turkey's army was rolling in more tanks into Syria on Thursday.
In the nearby Turkish city of Gaziantep, a fighter with one of the rebel factions involved in the Jarabulus offensive said that they would take on the Kurds as well if they had too.
The objectives of the operation included preventing the YPG establishing a contiguous territory across northern Syria, the fighter from the al-Jabha al-Shamiya faction told dpa on condition of anonymity.
Describing the powerful Kurdish forces as "a separatist group," he added: "If we must, we will also fight against the Kurds."
Among the rebel groups Turkey is backing in the offensive are ethnic Turkemn militias.
Despite the US support for the Turkish position in the area, the atmosphere inside Turkey remains largely anti-American, with pro-government newspapers sharply critical of Biden's trip to the country this week.
The spokesman for the US-led anti-Islamic State coalition says the Syrian Democratic Forces, a group comprising several factions but dominated by the Syrian Kurds, have moved back across the Euphrates River, to the east.
US Vice President Joe Biden says the Syrian Kurdish forces his country backs must go back across the Euphrates River to the east bank.
Syrian Kurds condemn the Turkish incursion into Islamic State-held Jarablus, calling it a "declaration of war."