A day earlier, Turkish airstrikes and missile attacks targeted positions of the Kurdish fighters on areas on the Syrian-Iraqi borders, killing 50 on both sides of the borders.
There was no immediate information on casualties, said the Observatory's Rami Abdel Rahman.
In a rare rebuke to a North Atlantic Treaty Organisation ally, the US military charged that Turkish airstrikes against a valued USA -backed Kurdish militia in northern Syria came with little warning and could have endangered American advisers.
Ankara has bombed the YPG in northern Syria for months, calling it a "terrorist" group because of its ties to the outlawed Kurdistan Workers' Party (PKK), which has been waging a deadly insurgency against Turkey since 1984.
The YPG Central Command also confirmed causalities among YPG members and civilians.
President Recep Tayyip Erdoğan said that Turkey informed Russian Federation, the USA and Northern Iraq before conducting airstrikes.
"We believe that among the Syrian Democratic Forces fighting ISIS effectively on the ground those forces that are made up of Syrian Kurds are not related to the PKK. We have no secret agenda", Cavusoglu told reporters in Uzbekistan. The Turkish airstrikes on Tuesday killed 20 members of the People's Protection Units, or YPG, in Syria, and five peshmerga fighters in Iraq. Kurdish sources said that 20 fighters died in the attack.
And Russia said Turkey's behaviour was cause for "serious concern".
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"We consider such actions unacceptable and going against the founding principles of worldwide relations", the Russian foreign ministry said, calling for "all sides to show restraint" and focus on fighting terrorism. Turkey has said the strikes were conducted to prevent infiltration of Kurdish rebels, weapons, ammunition and explosives from Syria and northern Iraq into Turkey.
Damascus said the bombardment was "a flagrant aggression by (President Recep Tayyip) Erdogan's regime on Syrian territory".
Erdogan said in an interview with Reuters that the strikes on Sinjar were aimed at denying a base to the PKK, and that Turkey had informed its counterparts in the coalition of its plans.
Turkish Prime Minister Binali Yildirim called the head of Iraq's Kurdish region Massud Barzani to express his condolences and sadness over the deaths, the Anadolu news agency said.
Along with the 28 believed to have been killed in the Syrian strikes - a lot of them YPG fighters - six pro-Ankara Kurdish peshmerga fighters were also killed in northern Iraq on Tuesday, in what was apparently an accident.
She accused the Turkish government of sparking the latest clashes in an attempt to distract from its weakened position after the slim referendum victory.
"We don't want to open a front with Turkey because the situation in Syria is complicated and we're fighting a terror group that is a threat to all mankind", she said, referring to Isis. "This is an act against the Kurdish people and against plans or a resolution in Syria".
"The coalition must take a stand", she added. "Words are not enough".
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