The attacks come just days after Ankara blamed the Kurdistan Workers' Party (PKK) for last Sunday's deadly bombing in central Istanbul.

"#Kobane, the city that defeated ISIS, is subjected to bombardment by the aircraft of the Turkish occupation," tweeted Farhad Shami, a spokesman for the Kurdish-led Syrian Democratic Forces (SDF).

Turkey considers the Kurdish People's Protection Units (YPG) -- the main component of the SDF -- an extension of the outlawed PKK.

Shami said there had also been air strikes against two densely populated villages in the north of the northern province of Aleppo and in the northeastern province of Hassakeh.

The Britain-based Syrian Observatory for Human Rights reported that the Turkish military had carried out more than 20 air strikes across the two provinces. The group has an extensive network of contacts across Syria.

Kobane, a Kurdish-majority town in Syria near the Turkish border was captured by the self-styled Islamic State group in late 2014, before Kurdish fighters drove them out early the following year.

Both the PKK and the YPG have denied any involvement in the Istanbul attack, in which six people were killed.

But Turkish Interior Minister Suleyman Soylu has said Ankara believes the order for the attack was given from Kobane, controlled by Syrian Kurdish militia forces in northern Syria.