Al-Foua and Kefraya, which represent the last remaining besieged population in Syria according to the United Nations, were attacked by the terrorists overnight, SANA news agency reported.
The report added that al-Foua and Kefraya’s defense forces repelled the dawn attack.
Fighting on the edge of the towns began early morning Friday, shortly after airstrikes carried out by Syrian warplanes on the village of Zardana in northeast Idlib killed at least 51 terrorists.
The so-called Syrian Observatory for Human Rights also confirmed the attack, saying, “The overnight attack on al-Foua and Kefraya was the fiercest in three years”.
On Sunday, heavy airstrikes struck a number of opposition-held positions near al-Foua and Kefraya, including the town of Binnish, and further afield in Idlib province, the Observatory added.
Last year, the Syrian government and militants reached a deal, known as the "Four Towns Agreement," that allowed the evacuation of residents of the two towns.
In return, people in two militant-held towns near Damascus, Madaya and Zabadani, were given safe passage to evacuate to territories under the control of terrorists or the Syrian government.
Takfiri terrorists have lost much of the territory they once held in Syria amid sweeping gains by government forces on the ground.
In April, Syrian forces managed to retake the Eastern Ghouta and Eastern Qalamoun regions near the capital.
For years, the areas had served as a launch pad for deadly terror attacks against civilians in Damascus.
Syrian forces later moved to liberate other militant-held areas in the provinces of Homs and Hama.