Syria's defence ministry and the Kurdish-led Syrian Democratic Forces traded blame over an attack in the northern city of Manbij on Saturday, casting a shadow over a landmark integration deal they signed in March, France 24 reported.

The defence ministry accused the SDF of carrying out a rocket barrage on one of the army's outposts in the city's countryside, injuring four troops and three civilians, according to the state news agency SANA. It described the attack as irresponsible and without justification.

The US-backed SDF said in a statement they were responding to "an unprovoked artillery assault targeting civilian-populated areas with more than ten shells" from factions operating within Syrian government ranks. The statement made no mention of any casualties.

In March, the SDF signed a deal with the Damascus Islamist-led government to join Syria's state institutions.

The deal aims to stitch back together a country fractured by 14 years of war, paving the way for Kurdish-led forces that hold a quarter of Syria to merge with Damascus, along with regional Kurdish governing bodies.

However, the deal did not specify how the SDF will be merged with Syria's armed forces. The SDF has previously said its forces must join as a bloc, while Damascus wants them to join as individuals.

A Turkish defence ministry source said last month the SDF must prove it is adhering to the agreement with the Syrian government. Ankara deems the SDF an extension of the outlawed Kurdistan Workers Party.

"While we reaffirm our commitment to respecting the current de-escalation arrangements, we call on the relevant authorities in the Syrian government to take responsibility and bring the undisciplined factions under their control," the SDF said in its statement.