Turkish-backed Syrian rebels say they are now advancing towards Manbij in northern Syria, a city captured earlier this month by Kurdish forces, as the US condemned the weekend clashes between the sides as "unacceptable".
Turkey's military said on Monday that the Ankara-backed Free Syrian Army (FSA) had cleared fighters from 10 more villages in northern Syria, as part of a cross-border offensive that had already captured a string of settlements south of the Syrian frontier town of Jarablus.
The statement did not say whether these fighters belonged to the Islamic State of Iraq and the Levant (ISIL) group or Kurdish forces.
"After seizing control of the border town of Jarablus, the FSA fighters moved under Turkish air cover to control villages such as Amarna, Yousef Beq and Ain al-Baida within hours," Al Jazeera's Hashem Ahelbarra, reporting from Gaziantep on the Turkish side of the Syria-Turkey border, said.
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"But their main target is to take over Manbij," he said. "YPG fighters maintain a significant presence along that area with their local allies."
Just weeks ago, Kurdish and Arab fighters, backed by US coalition air strikes, drove ISIL fighters out of Manbij after months of fighting.
Turkish forces have been pressing on with a two-pronged operation inside Syria against ISIL (also known as ISIS) fighters and the Syrian Kurdish People's Protection Units (YPG) since Wednesday, shelling more than a dozen targets.
"Taking on the YPG is a risk for the Turkish government," said our correspondent. "The Kurdish group is a crucial ally for the US in its fight against ISIL in Syria."
Meanwhile, the US Department of Defence condemned the clashes between Turkish forces and the YPG on Monday, calling them "unacceptable".
Ankara said it had killed 25 Kurdish "terrorists" in strikes on YPG positions on Sunday, a day after a Turkish soldier died in a rocket attack it blamed on Kurdish forces
On Monday, the Pentagon called the clashes "unacceptable" and urged an immediate de-escalation.
"We want to make clear that we find these clashes - in areas where ISIL is not located - unacceptable and a source of deep concern," said Brett McGurk, US special envoy for the fight against ISIL, also known as ISIS.
"We call on all armed actors to stand down," he wrote on Twitter, citing a US Department of Defense statement.
Later on Monday, Ash Carter, the US defense secretary, urged Turkey to not target Kurdish elements of Syrian rebels.
"We have called upon Turkey ... to stay focused on the fight against ISIL and not to engage Syrian Defense Forces, and we've had a number of contacts over the last several days," Carter told reporters.
Turkey's operation aims to push the YPG back across the Euphrates River to prevent it from joining up the region east of the river already under its control with a Kurdish-held area to the west.
US Vice President Joe Biden, visiting Ankara last week, said Washington had told the YPG to go back across the Euphrates or risk losing American support.
After Biden's warning, Kurdish officials seemed to have acceded to Turkish demands and said they withdrew the YPG forces from Manbij.
"The YPG said they have withdrawn to the East," said Al Jazeera's Ahelbarra. "But activists on the ground doubt that."
Ankara also said it had seen no evidence of this.
Mevlut Cavusoglu, Turkey's foreign minister, said on Monday the YPG "needs to cross east of the Euphrates as soon as possible. So long as they don't, they will be a target.
"In the places where it has moved, the YPG forces everyone out - including Kurds - who do not think like it does and carries out ethnic cleansing," he added.
Cavusoglu said the ethnic composition of the area around the city of Manbij was largely Arab.
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Deputy Prime Minister Numan Kurtulmus on Monday also confirmed one of the key aims of Turkey's operation in northern Syria was to prevent the creation of a corridor stretching from Iraq to the verge of the Mediterranean controlled by the YPG.
"If that happens, it means Syria has been divided," he was quoted as saying by Turkish broadcaster NTV.
He added that all relevant parties had been informed of Turkey's operation in Syria, including the government of President Bashar al-Assad.
But Kurtulmus denied Turkey was at war. "We are not pursuing an aim of becoming a permanent power in Syria. Turkey is not an invader. Turkey is not entering a war."
"It’s unclear whether Turkish commanders will send ground forces all the way to Manbij to help the FSA take control of the city or only provide air cover, said Al Jazeera's Ahelbarra.
"Either way, the conflict has become deepened with multiple frontlines and agendas at play."
|Syria war map territory, August 29 [Al Jazeera]
Source: Al Jazeera News and agencies