Lately there has been heavy fighting near Khan Sheikhoun between Damascus forces and the group controlling the city, predominantly the Islamist group Hayat Tahrir al-Sham (HTC), formerly known as Nusra Front.
The advance on the town, which has been in rebel hands since 2014, threatens to encircle and expel insurgents from their only patch of territory in neighbouring Hama province.
Idlib province is the last major anti-Assad stronghold in Syria after eight years of war.
Turkey did not say who conducted the airstrike but at least partially blamed Russian Federation.
Turkey, which hosts some 3.6 million Syrian refugees and warns it cannot accept more, fears the onslaught in Idlib could spark a new influx.
"Turkish vehicles loaded with munitions. are heading toward Khan Sheikhun to help the terrorists. which confirms once again the support provided by the Turkish regime to terrorist groups", a foreign ministry source quoted by the state news agency SANA said.
Syrian activists say that airstrikes halted a Turkish military convoy carrying ammunition after it crossed into northern Syria earlier in the day, bound for a rebel-held stronghold.
A colonel from a rebel faction confirmed to Reuters news agency that there were battles going on on the outskirts. On request from Russian Federation, the Syrian government agreed not to use force to retake the region to avoid casualties among civilians, who have blood ties with Turkey.
He said there was "international silence" over the surge of violence in Idlib, which he said raised the question of whether world powers had agreed on the offensive.
It wasn't immediately clear who was behind the strikes, Syrian or Russian warplanes.
The nature of the attacked convoy is perceived differently by the Syrian side, however. Damascus denies using such weapons.
Khan Sheikhun is a important strategic point as it links east, west and north Idlib.
Idlib is supposed to be protected from a massive government offensive by a Turkish-Russian deal struck in September a year ago.