Kurdish-led fighters were fending off Turkey's Syrian proxies in violent clashes on Sunday near the Kurdish-held town of Ain Issa in northern Syria, a Britain-based monitor said.

Pro-Ankara fighters have been stationed to the north of Ain Issa Turkish soldiers and their Syrian proxies seized a 120-kilometre stretch of territory along the border from Kurdish fighters in 2019.

Since then, pro-Turkish forces have engaged in sporadic skirmishes with the Kurdish-led Syrian Democratic Forces.

The latest fighting came as Syria's Kurds, who for years led the US-backed battle against the Daesh terror group in Syria, celebrated Nowruz to mark the advent of spring and Kurdish new year.

The clashes erupted as pro-Ankara fighters tried to advance north of Ain Issa on Friday after the SDF had cleared two villages of landmines to allow civilians to return, the Syrian Observatory for Human Rights said.

"But the SDF have until now prevented the pro-Ankara fighters from gaining any ground," Observatory head Rami Abdel Rahman said.

There was no immediate death toll for the clashes.

SDF spokesman Kino Gabriel said the Ain Issa area was under heavy attack, including by Turkish mortars, shelling and air strikes, but the Kurdish-led fighters had so far thwarted "infiltration attempts".

Turkey's defence ministry said Sunday its troops had retaliated after Kurdish fighters "opened fire on our special forces" from the south of the Turkish-held border strip.

Turkish air strike? 

The observatory, which relies on sources inside Syria, late Saturday reported a Turkish air strike on the village of Saida north of Ain Issa, saying it was the first in the area since 2019.

But Turkish security sources denied carrying out any air raid, accusing the Kurds of trying to spread misinformation.

Ankara considers Syrian Kurdish fighters to be a "terrorist" extension of the Kurdistan Workers' Party (PKK), which is outlawed in Turkey.

Syria's civil war has evolved into a complex conflict involving world powers and extremists since it started in 2011.

In the north of the country, Turkey and its Syrian proxies control several pockets of territory following three military incursions since 2016 against Daesh and Kurdish fighters.

They also include the northwestern region of Afrin, and an area around the city of Al Bab in northern Syria.

Almost two years ago, the SDF expelled Daesh from their last scrap of territory in the eastern riverside hamlet of Baghouz, taking thousands of alleged extremists and families members into their custody.

The extremist group however maintains a presence in eastern Syria and continues to carry out sporadic attacks