The ringleader of the U.S.-backed Syrian Democratic Forces (SDF), which is dominated by the PKK's Syrian offshoot YPG, said Thursday that the integration of the group's military, security and administrative structures into Syrian state institutions had been completed, marking a new stage in Damascus' efforts to restore state authority across the country.

An agreement reached with the Damascus government in January provided for the integration of the SDF's military and civilian institutions into the Syrian state, following clashes in which government forces regained significant territory previously held by the group.

"I want to say that the phase of integrating military, security and administrative institutions into national state institutions is complete and finished," Ferhat Abdi Şahin, code-named "Mazloum Kobani," said at an event in Qamishli in northeastern Syria.

"From now on, we begin a new phase."

The announcement follows months of negotiations over implementing the agreement, which sought to bring separate administrative and armed structures under the authority of the central government.