Turkish President Recep Tayyip Erdogan announces the military operation in Syria's Afrin has "actively" started. (AFP photo)

ANKARA, Jan. 20 (Xinhua) -- Turkish President Recep Tayyip Erdogan announced on Saturday the military operation in Syria's Afrin has "actively" started.

"The Afrin operation has actively begun on the field. The Manbij operation will follow," he said during a televised speech in the Aegean province of Kutahya.

Erdogan said that Turkey is determined to ensure its national security and to clear its borders of the People's Protection Units (YPG), which is considered by Ankara as the Syrian affiliate of the Kurdistan Workers' Party (PKK).

"Then we will step by step clear the terrorist elements from Manbij towards Iraqi border," the Turkish President said, noting that the United States has not kept its promise of withdrawing YPG militia in Manbij after their fight with the Islamic State (IS).

He slammed the U.S. decision to establish a new border army with the YPG fighters in order to secure Turkish and Iraqi borders with Syria.

Erdogan said the statements from Washington were contradictory. "We do not care about what they say. We only consider what happens on the ground," he said.

Turkish army has already been shelling against the YPG over the last two days from the positions in Cilvegozu region of the Turkish side of the border and Azaz region in Syria, next to Afrin where Turkish-backed Free Syrian Army fighters are located.

The Turkish army said on Saturday the army hit the shelters "within the scope of legitimate self-defense."

The PKK, listed as a terrorist organization by Turkey, the European Union and the United States, has been conducting armed violence against Ankara since July 2015 after a brief reconciliation period.