Rescue workers used bulldozers to remove the rubble and extract trapped people from the flattened buildings, the correspondent said.
But the cause of the blast was "not yet clear", Abdel Rahman added.
He said most of those killed were family members of fighters from Hayat Tahrir al-Sham (HTS), an alliance led by jihadists from Syria's former Al-Qaeda affiliate, who had been displaced to the area from the central province of Homs.
White Helmet rescue workers attempted to lift part of a floor of one of the buildings with a tall crane. Nearby three young boys watched on in silence, perched on a rock.
Behind mounds of rubble, the facade of a building was scorched black, due to a fire after the blast.
A civil defence source told AFP that women and children were among the dead. But rescue workers had pulled out "five people who were still alive", the source said.
In recent months, a series of explosions and assassinations -- mainly targeting rebel officials and fighters -- have rocked the province.
While some attacks have been claimed by IS, most are the result of infighting since last year between other groups.
In recent days, regime forces have ramped up their deadly bombardment of southern Idlib and sent reinforcements to nearby areas they control.
On Thursday, government helicopters dropped leaflets over towns in Idlib's eastern countryside urging people to surrender.
The United Nations appealed the same day for talks to avert "a civilian bloodbath" in the province.
Jan Egeland, head of the UN's humanitarian taskforce for Syria, said: "The war cannot be allowed to go to Idlib."
Around 2.5 million people live in the province, half of them displaced by fighting in other regions of the country.
More than 350,000 people have been killed and millions displaced since Syria's civil war started in 2011 with the brutal repression of anti-government protests.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)