Move comes after Turkey announces start of 'Operation Olive Branch'.
According to Anadolu Agency reporters on site, FSA fighters backed by Turkish military started to move towards the northern Syrian city in the early hours.
The Turkish General Staff confirmed earlier it launched “Operation Olive Branch” on Saturday at 5 p.m. (1400GMT).
"108 targets, which were used as shelters, hideouts and ammunition depots by terrorist organizations PKK/KCK/PYD-YPG and Daesh in seven areas, were destroyed by the air force," the military said in a statement late Saturday.
The operation was being carried out under the framework of Turkey’s rights based on international law, UN Security Council’s decisions and self-defense rights under the UN charter, the military added.
The statement said the operation will also take sensitivity into account and no civilian or innocent person would be harmed.
The PYD/PKK is the Syrian offshoot of the PKK terrorist group, which has been designated as a terrorist organization by Turkey, the U.S. and the EU.
Since the mid-1980s, the PKK has waged a wide-ranging terror campaign against the Turkish state in which an estimated 40,000 people have been killed.
Afrin has been a major hideout for the PYD/PKK since July 2012 when the Assad regime in Syria left the city to the terror group without putting up a fight.
The Turkish cities of Kilis and Hatay across the Syrian border are within the firing range of the PYD/PKK group from Afrin, which sits atop a hill. The terror group has also used Amanos Mountains to penetrate from Syria into Turkey.
The PYD/PKK depends on Afrin to connect to the Mediterranean from northwestern Syria. The terrorist organization also threatens Idlib deescalation zone over Afrin. A quarter of Syria land and 65 percent of Turkey-Syria border is under occupation of the terrorist organization.