Militants from the PKK terrorist organization’s Syrian offshoot, the U.S.-backed YPG, clashed with Assad regime forces in northeast Syria in a rare incident on Tuesday, a war monitor reported.

"Two regime soldiers were killed and others were wounded," while two members of an SDF-affiliated "military council" in Tal Tamr died after an "armed clash" in the area, the Syrian Observatory for Human Rights said. SDF is the umbrella group that is dominated by the YPG.

The pro-regime SANA news agency said that a "patrol of U.S. forces accompanied by members of the SDF militia tried to penetrate points controlled by the Syrian army" in Hassakeh province.

It did not mention whether there were victims but said the SDF attacked after soldiers blocked the patrol's passage.

The SDF confirmed two terrorists were killed in a statement to the French Press Agency (AFP). It did not mention the presence of Americans, and called the incident "a dangerous provocation by the Syrian regime."

The war in Syria is estimated to have killed nearly half a million people and displaced millions more since it began with a brutal crackdown on anti-government protests in 2011.

It quickly spiraled into a complex conflict that pulled in numerous actors, including terrorist groups and foreign powers.

Russia intervened militarily in Syria more than six years ago to shore up Bashar Assad.

Moscow had been trying to act as a mediator for Damascus and the YPG.

In the Syrian conflict, the YPG has been a key partner of the U.S. against the Daesh terrorist group, despite its NATO ally Turkey's legitimate security concerns.

When Turkey launched its cross-border Operation Peace Spring in late 2019, the YPG was forced to seek help from Damascus and its ally Russia to stem the attack, leading to the deployment of regime and Russian forces to the area.

YPG forces still control a large part of the northeast of the war-torn country, but regime forces are also present there, including in the main regional cities of Hassakeh and Qamishli. Damascus and the YPG have mostly coexisted during nearly a decade of conflict.

In 2021, however, tensions rose with each side accusing the other of imposing steep levies or restricting the movement of goods to areas under their respective control.