U.S. troops patrolling Turkish-Syrian border

Video from northern Syria showed the USA patrols alongside Kurds flying the People's Protection Units flag.

Turkish President Recep Tayyip Erdogan on Sunday threatened to strike Kurdish militants in Iraq and Syria, as the US -backed forces in Syria closed in on the last neighborhoods of a former stronghold of the Islamic State extremist group.

The agency said the relocation comes after Turkish officials announced the completion of a phase of Turkey's cross-border operation Euphrates Shield in Syria, adding the force may be used against Syrian Kurdish fighters "if needed".

Kurdish officials describe the US troop movement as a "buffer" between them and Turkey, according to the Associated Press, while USA officials say it's part of its cooperation with the Kurdish forces against ISIS in Syria. Those patrols followed a Turkish airstrike against bases of Syrian Kurdish militia, Washington's main ally in combating Islamic State militants in Syria. Although there are ideological ties between YPG and PKK, YPG says it is a separate group and the US government agrees. "The U.S. role has now become more like a buffer force between us and the Turks on all front lines", Mustafa Bali, identified as a Kurdish activist, told the AP, calling it a "warning message" to both sides to keep the focus on fighting the Islamic State (ISIS) and not each other.

In a second statement on Friday, the Turkish military said 10 Kurdish militants, five of whom were women, had been killed in operations in the southeastern province of Tunceli.

"We will be forced to continue (our offensives)", Erdogan said.

Ankara views the US -backed Syrian Kurds as a terror organization and an extension of Kurdish militants waging a three-decade-long insurgency against the Turkish state. The Turkish military reported 11 Kurdish "terrorists" killed.

Erdogan said that his government was "seriously saddened" by images showing USA military vehicles operating close to the border with Syrian Kurdish fighters, threatening further military action against the YPG.

A senior Kurdish official, Ilham Ahmad, also told AP that the USA forces began patrolling the border region Thursday in addition to their reconnaissance flights in the area.

Syrian government forces backed by Russian Federation also operate in the area. The town is mostly controlled by Kurdish forces, but Syrian government troops hold pockets of territory there, including the airport. Both Syrian YPG and Iraqi Peshmerga Kurdish militias condemned the attack.

Ankara is keen to join any US-led operation to clear Raqa of IS militants, but without Syrian Kurdish militia forces. The Kurdish Regional Government said that Turkey did it by mistake and blamed the PKK for the deaths by operating in the area. "I could not possibly be more thrilled than to be more than 100 miles way from Washington's swamp", Mr. Trump said to cheers, as he began his speech by verbally smacking the news media, drawing the chant of "CNN sucks!" from the crowd. The US has been complaining that Turkey has been carrying out attacks without any coordination with their coalition partners.

Erdogan's comments come ahead of a meeting with President Donald Trump on May 16 in the United States, their first face-to-face summit since the American leader took office in January. However, the US has called the PYD a key ally in the fight against Daesh in Syria.

Tension between Turkey and the YPG has been rising.

The US classes the PKK as a terrorist organisation, but is supporting the Syrian Democratic Forces - which encompassed the YPG, on the ground. "If the coalition does not show a concrete reaction, then we will withdraw our forces from Raqqa", she told a local Kurdish media.