IS massacre in Syrian villages 'left open to attack'
The attack on the villages of Aqarib and al-Mabuja left at least 15 civilians and 27 regime fighters dead, while another ten were unidentified.
Fifteen IS militants were also killed in the dawn raid, while state-run SANA news agency reported that 20 civilians were killed in Aqareb.
Most of the civilians had been beheaded and their bodies mutilated, SANA said.
The regime media outlet released a photo showing the bloodied remains of the alleged victims.
SANA said regime forces prevented IS from advancing deeper into the valley, while the remaining fighters fled to the desert.
Observatory Director Rami Abdel Rahman said a man and his two children were murdered by the miltitants, and said IS had seized control of Aqarib and part of Mabuja.
"Despite the arrival of reinforcements, government forces have been unable to repel the attack so far," Abdel Rahman told AFP.
Residents in the two villages took up arms in 2015, after pro-regime militias repeatedly fled the area leaving families vulnerable to attack.
Fighters from the regime-sponsored National Defence Forces repeatedly stole from locals and put up little resistance to IS assaults, The New Arab reported in 2015.
It mirrored trends in other regime-held areas where locals formed their own militias after being unconvinced by the Syrian army' ability to defend their homes from IS attacks.
IS has attacked Mabuja before, murdering 37 civilians in the village which is made up of Sunnis, Ismailis and Alawites.
The militants also kidnapped at least 50 civilians, half of them women, in the east Hama region.
Agencies contributed to this story.