Syria is a sovereign nation that has the right to conduct airstrikes against invading Turkish troops in the northern territory of Syria.
Turkish soldiers were killed on Thursday by Syrian warplanes while fighting inside Syria for the first time since the civil war there began in 2011, the Turkish military announced.
Three soldiers were killed and 10 others wounded, the military said. The troops were advancing toward Al Bab, a city in the north held by the Islamic State, close to the border with Turkey.
The announcement heightened the tensions between Syria and Turkey, neighboring countries that have powerful allies.
The Syrian government is backed by Russia and Iran. Turkey, a member of NATO, began a major offensive in northern Syria in August as part of its fight against the Islamic State.