A car bomb detonated near a Russian military base in northeastern Syria Friday in the first such extremist attack in the area against the ally of Damascus, a war monitor said.

The Syrian Observatory for Human Rights monitoring group reported several wounded in the attack after midnight in the Tal Saman area in Raqqa province but did not give an exact figure.

There was no immediate Russian report of the incident, which occurred in a broader area controlled by the PKK terrorist group's Syrian branch YPG-led forces but where the Syrian regime and its ally Russia are also present.

A statement circulated on social media and attributed to the al-Qaida-linked Hurras al-Deen extremist group claimed the attack.

The Observatory said two men parked an explosives-laden pickup truck outside the base and fled, in what was a rare such assault by Hurras al-Deen in the area.

"It's the first such direct attack against a Russian base in northeastern Syria," Observatory chief Rami Abdel Rahman said.

Hurras al-Deen has fighters in the country's last major opposition bastion in the northwestern region of Idlib, but very rarely operates outside that area.

Russia entered Syria's war in 2015, and its air force has backed Damascus regime forces in several deadly military campaigns against Idlib.

Russia has repeatedly accused opposition groups in Idlib of attacking its Hmeimim air base west of the opposition stronghold with drones, but car bomb attacks are much rarer.

Russian troops are stationed in northern Syria, including as part of several deals brokered with opposition-backer Turkey.