Dozens reported dead as Turkish air strikes hit towns in northern Syria and Iraq
The Kurdish-led authorities that control much of northern Syria said the dead included 11 civilians, 15 Syrian government fighters, two silo guards and a Kurdish fighter.
The Syrian Observatory for Human Rights, a UK-based activist group that has an extensive network of sources in Syria, said the strikes had killed 18 members of the Kurdish-led Syrian Democratic Forces (SDF) and 12 members of Syria's military.
The Observatory also reported the death of a journalist, Issam Abdallah, Syrian correspondent for a Kurdish news agency.
The Syrian government-backed news agency Sana confirmed the death of several Syrian soldiers, without specifying the number.
The air strikes were carried out on Saturday evening and before dawn on Sunday.
Turkey's defence ministry said on Sunday that the strikes had targeted Qandil, Asos and Hakurk in Iraq and Kobane, Tal Rifat, Cizire and Derik in northern Syria.
The ministry said that 89 targets, including shelters and ammunition depots, were destroyed in the air strikes.
One Turkish soldier and two police were wounded as result of a rocket fired at Turkey's Syrian border province of Kilis on Sunday, Turkey's state-owned Anadolu Agency reported.
Anadolu said the rocket hit an area near a border gate but did not elaborate further.
In a statement earlier on Sunday, the SDF had said it would respond to the attacks "effectively in the right time and place".
'Hour of reckoning'
The strikes come just days after Ankara blamed the Kurdistan Workers' Party (PKK) for last Sunday's deadly bombing in central Istanbul. Turkey said on Tuesday that it planned to pursue targets in northern Syria after it completed a cross-border operation against the group.
"#Kobane, the city that defeated ISIS, is subjected to bombardment by the aircraft of the Turkish occupation," tweeted Farhad Shami, a spokesman for the SDF, referring to the Islamic State group of militants.
Turkey considers the Kurdish People's Protection Units (YPG), the main component of the SDF, an extension of the outlawed PKK.
The PKK and SDF have denied any involvement in the Istanbul attack, in which six people were killed and 80 wounded.
The Turkish defence ministry had tweeted late on Saturday that "the hour of reckoning has come" with a photo of a fighter jet taking off.
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.