Aleppo regime offensive
A member of the Syrian government forces talks on the phone as he patrols after they took control of the village of Kiffin, on the northern outskirts of the embattled city of AleppoGeorge Ourfalian/AFP/Getty Images

Turkey shelled Kurdish militants who were in Syria, in a move that threatens to further escalate the raging conflict. Monitors said Turkish artillery was targeting areas north of Aleppo recently seized by the Kurdish People's Protection Units (YPG) from Islamist rebels.

The Syrian Observatory for Human Rights said the Menagh air base and YPG positions near the town of Azaz came under bombardment on 13 February. The attack was confirmed by the YPG, which posted online an aerial picture of a targeted area, and by Turkish government sources speaking to Reuters. There were no immediate reports of casualties.

Loud explosions could be heard in online footage purportedly depicting Turkish artillery firing across the border.

Earlier this week, the YPG advanced into rebel-held territory north of Aleppo exploiting an offensive in the same area by forces loyal to the Assad regime backed by heavy Russian airstrikes. The government advance displaced tens of thousands of people that have fled towards the Turkish border, creating a new humanitarian emergency.

The development deepened the diplomatic quagmire in Syria just days after world powers agreed to seek a nationwide "cessation of hostilities" within a week. Ankara, a Nato member, views the YPG as a proxy of the Turkey-based Kurdistan Workers' Party (PKK), which is leading an insurrection against the government and is considered a terrorist organisation also by the US and the EU.

At the same time, the YPG is a key Western ally against the Islamic State (Isis) on the Syrian battleground. The shelling came after Turkish Prime Minister Ahmet Davutoglu said Turkey and Saudi Arabia were considering a possible joint ground operation against the Isis (Deash).

The development deepened the diplomatic quagmire in Syria just days after world powers agreed to seek a nationwide ceasefire within a week. Ankara, a Nato member, views the YPG as a proxy of the Turkey-based Kurdistan Workers' Party (PKK), which is leading an insurgency against the government and is considered a terrorist organisation also by the US and the EU.