The American patrol was accompanied by Kurdish SDF forces, the main US ally in the years-long battle against ISIL.

US forces patrolled part of Syria’s border with Turkey on Thursday in the first such move since Washington withdrew troops from the area earlier this month.

American infantry troops and tanks also arrived in Syria’s Deir Az Zor region and are expected to head to the northeast, where US President Donald Trump has vowed to secure oilfields under the control of its Kurdish ally, Syrian Democratic Forces (SDF).

Five armoured vehicles bearing US flags patrolled a strip of the frontier north of the town of Qahtaniyah. The patrol was seen by an AFP news agency correspondent and the SDF confirmed the military activity to Reuters news agency.

The American patrol was accompanied by Kurdish SDF forces, the main US ally in the years-long battle against the Islamic State Iraq and the Levant (ISIL or ISIS).

BREAKING: Bradleys & infantry troops from the 30th Armored Brigade Combat team, a National Guard unit from South Carolina, arrived in the Deir ez Zour region in Syria in the past few hours, according to CG of Operation Inherent Resolve, Lt Gen Pat White. — Courtney Kube (@ckubeNBC) October 31, 2019

US forces used to patrol the section of the border north of Qahtaniyah before Washington announced its controversial pullback on October 6.

Thursday’s move came as heavy fighting between Syrian army troops and Turkish forces erupted a day earlier near Ras al-Ain, as Turkish-backed forces seized villages surrounding the border town.

The violence underscores the risk of full-scale fighting in northeast Syria resuming after Ankara struck separate deals with Washington and Moscow to push the Syrian Kurdish militia People’s Protection Units (YPG) – which spearheads the SDF – at least 30km (19 miles) south of the border.

Thousands of civilians flee

Turkey’s military crossed into northeast Syria on October 9 to attack the YPG after Trump’s abrupt withdrawal of US forces there days earlier.

Turkish-backed rebels said there were intermittent clashes in recent days south of Ras al-Ain, which Turkey seized from Syrian Kurdish-led forces earlier this month.

Al Jazeera’s Hashem Ahelbarra, reporting from the border town of Sanliurfa, said thousands of people were fleeing the fighting near Ras al-Ain and Tal Tamr towns.

Turkish-backed Syrian opposition fighters – known as the Syrian National Army (SNA) – launched an offensive and took over areas previously under control of Kurdish fighters south of Ras al-Ain, he said.

As fighting intensified, Syrian troops deployed reinforcements from Derbasiyah to Tal Tamr.

“The SNA took over western parts of the town. People have had enough each time someone controls the area and ends up being worse than the previous armed group,” one Tal Tamr resident told Al Jazeera.

“I am concerned for my children, this is why I am leaving. The Syrian army is on the front line to stop the rebels’ offensive, but you never know.”

As part of Turkey’s deal with Russia, Syrian troops have with the agreement of Kurdish forces headed north to take up positions near the border, a region Damascus has not controlled since early on in the country’s eight-and-a-half-year-old war.

Joint Russian and Turkish troops plan to begin patrols 10km (6 miles) inside Syria on Friday.

Afrin attack

Meanwhile, at least eight people were killed on Thursday when a car bomb exploded in a busy market in the northwest Syrian city of Afrin, under control of Turkey-backed rebel groups, witnesses said. The blast also wounded at least 30 people.

The Turkish military, helped by its Syrian rebel allies, seized Afrin, a mainly Kurdish city, from the Kurdish YPG militia in March 2018 in a major offensive. Turkish forces have since carved out a buffer zone inside northern Syria that extends along most of the country’s border.

Videos posted on social media showed extensive damage to the market area with fires burning.

Similar car blasts frequently hit crowded civilian areas in the mainly Arab-populated towns near the border with Turkey under the control of Turkish-backed forces.

Residents and rebels in the rebel-held northwest blame the YPG for the attacks. The Kurdish-led forces say they are engaged in a guerrilla campaign against Turkish forces but deny they target civilians.