(CNN) Turkey's Defense Ministry has condemned an airstrike in northwestern Syria that killed three civilians and injured 12 others on Monday.

It said that the strike was launched at a Turkish convoy , though a Syrian opposition military commander and a Syrian opposition media activist told CNN the strike hit a Syrian opposition vehicle traveling with the Turkish convoy.

A Syrian media activist who arrived to the scene after the strike told CNN that the warplane was Syrian and that it struck a vehicle belonging to the National Liberation Army, which is part of the Turkish-backed Free Syrian Army (FSA).

The Turkish military convoy halted its travel due to the airstrike and then went southward to the town of Heish, which is approximately 11.2 kilometers (seven miles) north of Khan Sheikhoun, according to the media activist.

A separate media activist told CNN that there are fierce clashes between the FSA and the Syrian regime west of Khan Sheikhoun. A Syrian opposition source said Russian and Syrian jets are carrying out strikes on the highway that link Heish and Khan Sheikhoun in an apparent attempt to keep the convoy from advancing.

The Syrian government on Monday accused Turkey of heading to Khan Sheikhoun in order to "rescue the defeated Al Nusra Front terror group," Syrian state media SANA reported, citing a Ministry of Foreign Affairs official.

The international community has frequently accused the Syrian government of indiscriminate bombing in its fight against rebels since the start of the country's civil war. Hundreds of thousands of civilians are believed to have died in government offensives.