Jan. 21 (UPI) -- Turkey moved grounded units across the border into Syria Sunday to continue its offensive against U.S.-backed Kurdish militia in the area.
"Our units have entered Afrin from two branches," said Yildirim. "This means the land operation has begun."
The move comes a day after Turkish jets struck all but five of the 113 Kurdish militia targets as part of a four-phase offensive known as Operation Olive Branch.
Afrin is controlled by the People's Protection Units, which is largely a Kurdish militia known as the YPG that Turkey considers a terror group.
The goal of the operation is to create a 19-mile deep safe zone in the northwestern Afrin region of Syria to drive YPG forces out of the area, Yildirim told Turkey's state-run Anadolu Agency.
"First goal [of the operation] is to create a safe area there and then we can take concrete steps to eliminate terrorist elements," he said.
Yildrim said there are about 8,000 to 10,000 terrorists in Afrin including YPG and the Kurdistan Workers' Party, or PKK.
"The PKK, the YPG, the PYD are all the same. Changing their names does not change fact they are terror organizations," President Recep Tayyip Erdogan said during a public rally in Bursa Sunday.
Five missiles believed to be fired by YPG forces from Syria struck the Turkish border town of Reyhanli, killing one person and injuring 32 more.
U.S. State Department spokeswoman Heather Nauert said the United States is "very concerned" about Turkey's actions in Syria.
"We urge Turkey to show restraint and ensure its military operations remain limited in scope and duration and scrupulous to avoid civilian casualties," Nauert said.
Turkey said the operation is being carried out invoking self-defense under international law and solely targeting what it considers terrorist forces.