The Syrian government, backed by Russia, began bombarding the last rebel-held territory of Idlib in April.
Attacks were launched from territory controlled by Syrian government forces and were judged to have been carried out deliberately, Turkey’s Ministry of National Defence said in a statement late on Thursday.
The wounded were evacuated and receiving treatment, it added.
The Turkish military subsequently opened fire on Syrian government forces’ positions where the attacks were launched.
Syria and its ally Russia launched major operations in April in Syria’s rebel-held northwest, where Turkish forces also have a presence near their southern border.
The Ministry of National Defence said Russia’s attache in Ankara was summoned to the military headquarters and was told Thursday’s attacks will be “punished in the strongest way”.
‘Don’t want to fight’
Similar attacks were carried out on Turkish observation posts in the region earlier this month. After the previous attack, the Turkish military retaliated with heavy weapons.
Syrian Foreign Minister Walid al-Moualem said earlier that Damascus does not want to see any fighting with Turkey.
“We hope that our military and the Turkish military do not fight. This is our principled stance,” said al-Moualem. “What we are fighting is terrorists, especially in Idlib, which is Syrian territory – part of our country.”
Russia and Turkey, backers of rebels fighting in Syria, cosponsored a de-escalation agreement for the northwest region that has been in place since last year.
But the deal has faltered in recent months, with heightened fighting forcing hundreds of thousands of civilians to flee.
About 300 people have been killed by Syrian and Russian air raids and shelling in the area since late April, according to the United Nations, which has warned of a new refugee crisis with about three million people living in the region.
Idlib is the last remaining bastion for anti-government rebels after eight years of civil war.