Turkey’s army shelled positions held by Kurdish-backed fighters for the second straight day on Sunday in northern Syria, according to Al Jazeera.

The attack came after Turkey bombed the Kurdish militia Saturday and demanded that it retreat from the territory it had seized. Two fighters died in the Saturday incident, the Syrian Observatory for Human Rights, a U.K.-based monitoring group told Al Jazeera.

Turkey urged fighters with the Syrian Kurdish People’s Protection Units (YPG), the armed wing of the Syria’s Democratic Union Party (PYD), to retreat from the areas it captured in the northern part of Aleppo. The U.S., which sees PYD as a close ally in its fight against Islamic State group, urged Turkey to stop the shelling and focus on fighting the terrorist group.

“The PYD is trying to carry out an ethnic cleansing by raiding areas where there is no or little Kurdish population and works to remove non-Kurdish ethnic elements out of these areas,” Yasin Aktay, a government MP told Al Jazeera.

Turkey’s forces shelled the Menagh airbase and several other positions, which were seized on Thursday from Syrian Islamist rebels by YPG, a group seen as a terrorist organization by Turkey.

Prime Minister Ahmet Davutoglu reportedly said Saturday that the shelling had taken place under “the rules of engagement against forces that represented a threat in Azaz and the surrounding area.”

On Saturday, Turkey’s Foreign Minister Mevlut Cavusoglu said the country’s troops and Saudi Arabia might participate in a ground operation against ISIS. Saudi Arabia also confirmed late Saturday that it sent aircraft to Turkey’s Incirlik air base for the fight against ISIS militants.

World powers reached an agreement in Munich Friday to try to bring about a cessation of hostilities in Syria. However, neither the Syrian government nor the U.S. backed-rebels were involved in the deal, and both have since vowed to continue fighting.