The Turkish army shelled Kurdish militia in northern Syria for a second day on Sunday (February 14), while Russia made clear it would continue bombing Syrian rebel targets.
Major powers agreed on Friday (February 12) to a limited cessation of hostilities in Syria but the deal does not take effect until the end of this week and was not signed by any of the warring parties - the Damascus government and numerous rebel factions fighting it.
Russian bombing raids directed at terrorists groups are meanwhile helping the Syrian army to achieve what could be its biggest victory of the war in the battle for Aleppo, the country's largest city and commercial hub before the conflict.
The situation has been complicated by the involvement of Kurdish-backed combatants in the area north of Aleppo near the Turkish border, which has drawn a swift military response from artillery in Turkey.
The Kurdish YPG militia, helped by Russian air raids, seized an ex-military air base at Menagh last week, angering Turkey, which sees the YPG as an extension of the PKK, a Kurdish group that waged a bloody insurgent campaign on Turkish soil over most of the past three decades.
Turkey began shelling while demanding that the YPG militia withdraw from areas it has captured from Syrian rebels in the northern Aleppo region in recent days, including the Menagh air base. The bombardment killed two YPG fighters, according to the Syrian Observatory for Human Rights.
The Syrian Kurdish PYD party rejected Turkish demands for withdrawal, while the Syrian government said Turkish shelling of northern Syria amounted to direct support for insurgent groups.
Turkey has been alarmed by the expansion of Kurdish sway in northern Syria since the start of the conflict in 2011. The YPG controls nearly all of Syria's northern frontier with Turkey and has been a close ally of the United States in the campaign against ISIS in Syria.
Ankara views the group as an extension of the Kurdistan Workers Party (PKK), which has waged a three-decade-old insurgency for autonomy in southeast Turkey.
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