The bombing comes after Syrian government forces captured the strategic Abu Duhur air base last week
Government air strikes have killed 33 civilians in the past 24 hours in Syria's northwestern province of Idlib where government forces are fighting militants, a monitor said on Monday.
On Monday alone, the strikes killed 16 civilians including 11 in a vegetable market in the town of Saraqeb, the Britain-based Syrian Observatory for Human Rights said.
The 17 others were killed on Sunday in raids on various areas of the province, large parts of which are controlled by Hayat Tahrir al-Sham (HTS), which is dominated by Al-Qaeda's former Syria affiliate.
"Regime war planes have intensified their strikes over the past 24 hours after relative calm due to bad weather," Observatory chief Rami Abdul Rahman said.
Syrian troops had been advancing on Idlib as part of a fierce offensive launched in late December with Russian backing.
Is Afrin more important than Idlib and its villages - the last stronghold of the Syrian revolution in the north - which includes more than 5 million displaced people from different regions?
- Hayat Tahrir al-Sham
At the market in Saraqeb, an AFP correspondent saw pools of blood on the ground. Small trucks loaded with sacks of potatoes stood abandoned after their windows were blasted from their frames.
In front of a hospital in the town, a motorbike and a car were trapped below the rubble and twisted metal.
An alliance of militants and rebels overran the vast majority of Idlib province in 2015.
On 21 January, Syria's army said it had captured the vital military airport of Abu Duhur on the edge of Idlib province, in a breakthrough for the government in the last Syrian province beyond its control.
With the airport's capture, the army said, troops would secure a key route leading from the neighbouring province of Aleppo south to the capital Damascus.
HTS claimed that other rebel forces had abandoned Idlib to join in the Turkish fight against the pro-Kurdish People's Protection Units (YPG) in northwest Afrin.
"In response to the battles surrounding the Abu Duhur airport, a battle to liberate the city of Afrin from the Kurdish militias was launched. Thousands of fighters responded to them," said the group in a statement last week.
"Is Afrin more important than Idlib and its villages - the last stronghold of the Syrian revolution in the north - which includes more than 5 million displaced people from different regions?"
Syria's war has killed more than 340,000 people and displaced millions since it began in March 2011 with the brutal repression of anti-government protests.
The bombing came as a peace conference was set to begin in the Russian resort of Sochi, despite the opposition announcing they would not take part.
On Monday, the Kremlim shrugged off the opposition's decision, saying the event would go ahead regardless and make a meaningful contribution to finding a political solution.
Russia is hosting what it has called a Syrian Congress of National Dialogue in the Black Sea resort of Sochi on Tuesday that it hopes will launch negotiations on drafting a new constitution for Syria after almost seven years of civil war.
But Western powers and some Arab states believe Sochi is an attempt to create a separate peace process that would undermine UN efforts to broker a peace deal while laying the groundwork for a solution more suitable to Syrian President Bashar al-Assad and his allies, Russia and Iran.
Everyone recognizes that immediate breakthroughs in the Syrian peace process are unlikely to be possible. The only thing that is possible is patient, incremental, detailed work that can move us forward. In this sense, the Congress will be a very important, meaningful step on this road
- Dmitry Peskov, Kremlin spokesman
A spokesman for the Syrian opposition said on Saturday it would not attend the Russian event for those reasons, dismissing the gathering as an attempt by Moscow to sideline the UN-backed peace process.
The decision was a setback for Moscow, which is keen to cast itself and President Vladimir Putin as an important Middle East peace broker after its military helped turn the tide of the conflict in Syria in Assad’s favour.
Kremlin spokesman Dmitry Peskov said on a conference call with reporters on Monday that the opposition boycott would not seriously hinder the conference, however.
“The fact that some representatives of the processes currently taking place in Syria are not participating is unlikely to stop this congress from going ahead and is unlikely to seriously undermine the importance of the congress,” he said.
“Everyone recognises that immediate breakthroughs in the Syrian peace process are unlikely to be possible. The only thing that is possible is patient, incremental, detailed work that can move us forward. In this sense, the congress will be a very important, meaningful step on this road.”
George Sabra, a prominent figure in the Syrian political opposition, told Reuters by phone that the event was a cynical waste of time.
“(Sochi) is a project to serve Russian policy,” said Sabra. “The Russians are trying, through this congress, to find a place for themselves in the Syrian political space after putting their heavy hand on Syrian land.”