They added that the first blast occurred in a main street in the provincial capital on Monday after an explosive device planted under a parked car detonated.
Many of the casualties were civil defense workers who reached the area just moments before a second explosion nearby, which some witnesses attributed to a bomb rigged to a motorcycle.
According to the so-called Syrian Observatory for Human Rights (SOHR), which is close to Syrian opposition, the twin blasts wounded at least 25, Presstv reported.
Social media footage showed aid workers carrying away dead bodies and rescuing wounded civilians.
There was no immediate claim of responsibility for the attacks.
Foreign-backed militancy erupted in Syria in March 2011, breaking out into an all-out conflict that drew in a mix of international terrorists and paid mercenaries fighting against the Syrian government. But the conflict has been winding down as Damascus reasserts control over parts formerly held by militant and terrorist groups.
Idlib Province remains largely unsettled, because it remains a concentration point for armed groups. Over the past couple of years, armed groups that have been defeated in battles with the Syrian military have been bused into Idlib under agreements with Damascus. While those groups have mostly had to leave their heavy weaponry behind under the deals, they have been allowed to take their small arms with them.
Members of the Jabhat Fateh al-Sham Takfiri terrorist group, formerly known as al-Nusra Front, have reportedly moved barrels with banned chlorine to a town in Idlib Province, using vehicles of the so-called White Helmets, which claims to be a civil defense group.
“According to our data, several chlorine containers were transported from [the northwestern Syrian city of] Jisr al-Shugur to Khan Shaykhun town in the south of Idlib Province. The transportation took place under coordination and cooperation between the White Helmets and Jabhat Fateh al-Sham terrorists. The containers with the toxic substance were transported in two ambulances,” head of Damascus-based Syrian Human Rights Network, Ahmad Kazem, told Russia’s Sputnik news agency earlier this month.
In December, US President Donald Trump abruptly announced that his country had “defeated" Daesh Takfiri terrorists in Syria and would be pulling all 2,000 American forces from the country.
In an exclusive interview with RT Arabic on February 7, Iranian Foreign Minister Mohammad Javad Zarif warned about the current situation in Idlib Province, describing it as “very dangerous.”
“The situation in the Syrian province [of Idlib] is very dangerous, and the Nusra Front terrorist group – which is not part of a de-escalation zone – is controlling a majority of the province’s regions,” Zarif said.