If it is recaptured, the airport will be "the first military base in the hands of the regime in Idlib province", said Observatory director Rami Abdel Rahman.
The activist group reported that the Syrian army has now taken control of 120 villages in the Idlib province since the onset of their offensive on December 25, 2017. FSA rebels and the Nusra Front had been reported to have been fighting.
Idlib province is nearly entirely controlled by a jihadi outfit known as Hayat Tahrir al-Sham (HTS) consisting mostly of fighters from a former al-Qaida affiliate.More news: Time travel? Flight takes off in 2018, lands in 2017
The wide-scale counter-attack aims to foil the advance of the Syrian army and restore areas taken by the army in the northeastern countryside of Hama province in central Syria and the southeastern countryside of Idlib province in northwestern Syria. A Syrian military source denied this and dismissed rebel talk of a counter attack as propaganda.
The activists said the warplane belonged to the Syrian army.
Since losing the airbase in 2015 following a two-year jihadist siege, the Syrian government has only had control of two villages in Idlib province: Fua and Kafraya.More news: Classified US Satellite Launched from Vandenberg
The largest opposition-held area, Idlib has been under attack for many months with Syrian and Iranian forces escalating airstrikes and ground assaults in the past three weeks, resulting in a string of villages being won by the regime.
A day earlier, the Syrian Observatory for Human Rights monitor group said the Syrian army entered the southern part of Abu al-Duhur air base, adding that clashes were taking place inside the compound.
Almost 100,000 people have been displaced since early December by fighting in northwestern Syria, where the regime is waging an offensive against jihadis, the United Nations said on Wednesday.More news: Google acquired speaker tech startup past year
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