Jets pounded Zardana village in northwestern Idlib province, where a "de-escalation zone" was established during Astana peace talks between Turkey, Russia and Iran.
Air strikes on a village in Syria's opposition-held Idlib province have killed at least 44 people, the Syrian Observatory for Human Rights (SOHR) said on Friday.
"War planes, which are likely Russian, targeted the village of Zardana in northern rural Idlib overnight and caused the highest death toll in a single attack on the region since late March," Rami Abdulrahman, the director of the Britain-based war monitor said.
However, Russia denied that its war planes carried out the air strikes. The Russian Defence Ministry was quoted as saying it had information about fighting between Nusra Front militants and opposition fighters involving heavy artillery fire in the past 24 hours.
The death toll is expected to increase as some of the 50 injured in the strikes were in a critical condition, Abdulrahman said.
Rescue workers were still searching the rubble for survivors.
Mustafa Haj Yousuf, head of the local civil defence unit, told Anadolu Agency that five members of the civil defence unit were also among those injured when the strikes targeted a market and an area near a mosque.
“The air strikes were carried out by SU-24 Russian fighter jets from Latakia airbase,” the Syrian opposition said in a statement.
Injured civilians were taken to nearby hospitals.
An AFP correspondent at the scene saw volunteers and a crane continue to search the rubble for bodies in the early morning.
Half a dozen men in civilian clothes helped carry a person in a black body bag away from the site of the strikes, which pulverised several buildings.
During the night, dozens of wounded streamed in to the local hospital, including women, children, the elderly and rescue volunteers, the correspondent said.
The twisted bodies of the deceased lay covered in a fine light grey dust and dashed with bright red blood amid the rubble.
Idlib, under the control of anti-regime armed groups, was declared a "de-escalation zone" during peace talks between Russia, Turkey and Iran in Astana, Kazakhstan, in May last year.
Northwestern Idlib region is the largest populated area of Syria still in the hands of groups opposed to the Damascus regime of Bashar al Assad.
In recent years, tens of thousands of fighters and civilians have fled there from parts of the country which the Syrian army has recaptured with the help of Russia and Iran.
Despite Russia's agreement that Idlib is a de-escalation zone, the Assad regime and Russian forces regularly bomb the region.