Turkish soldiers and forces of the Free Syria Army celebrated on the streets of Afrin after they ousted Kurdish fighters from the town.
"We have left behind the most important stage of Operation Olive Branch"President of Turkey
The victory of the Kurdish fighting force known as the YPG, which Turkey considers to be a terrorist organisation, came after eight weeks of fighting in the surrounding province in northwestern Syria.
In a speech on Monday, Turkish President Recep Tayyip Erdoğan said the military operations would continue until Turkish-backed forces had secured all of Syria's Kurdish areas.
"By taking control of Afrin town centre yesterday we have left behind the most important stage of Operation Olive Branch," he said, referring to the name given by Turkish commanders to the Afrin operation.
"Next we will continue this process with Manbij, Ayn al-Arab, Tel Abyad, Ras Al-Ain and Qamishli until this corridor has been completely removed."
While news the capture was celebrated both in Ankara and Afrin, the United States said it was "deeply concerned" that it appeared the majority of Afrin's Kurdish population had evacuated under threat of attack by the arriving forces.
A State Department statement said: "This adds to the already concerning humanitarian situation in the area, with United Nations agencies reporting a displaced population in or from Afrin district in the hundreds of thousands, who now require immediate shelter and other assistance to meet basic needs.
"We are also concerned over reports of looting inside the city of Afrin.
"We have repeatedly expressed our serious concern to Turkish officials regarding the situation in Afrin."
Turkey considers the YPG to be an affiliate of the PKK, which has fought an insurgency within Turkish borders for the past four decades.