The air raids in the militant-run northwestern region of Idlib also wounded several others, the Syrian Observatory for Human Rights says.
Air strikes by Syrian regime and Russian forces killed at least 20 people in rebel-held northwestern Syria on Saturday, activists and the Syrian Observatory for Human Rights said.
The attacks hit five villages in the Idlib region of the northwest, part of the last major territorial foothold of the insurgency against Syrian regime leader Bashar al Assad.
Russian jets killed at least nine people in an attack that hit a market in the village of Balyoun and another four people in a strike on the village of al Bara, the Observatory said.
Five more people were killed in a barrel bomb attack by Syrian regime helicopters on the village of Abdita, the Observatory said.
Barrel bombs killed two more people in the villages of Jebghas and Tel Minis, it added.
The air raids in the militant-run northwestern region of Idlib also wounded several others, the Observatory said.
An AFP correspondent at the scene saw rescue workers pick through the rubble of a two-storey home whose concrete roof had collapsed.
Rescuers carried away the body of a victim wrapped in a blanket on a stretcher.
Syrian regime media carried no reports of military operations by the regime or its Russian ally in those areas on Saturday.
The Observatory said eight children were among the dead.
At least 11 people were killed in Syrian regime air strikes that hit two outdoor markets on Monday, the civil defence said.
The Britain-based monitor, which relies on a network of sources inside Syria, says it determines the provenance of an air strike by looking at flight patterns and the aircraft and munitions involved.
Control of Idlib
Russia and Turkey, which backs the Syrian opposition and has troops on the ground in Idlib, brokered a ceasefire in the northwest in August but attacks have continued since then.
The Idlib region, which is home to some three million people including many displaced by Syria's civil war, is controlled by the country's former Al Qaeda affiliate.
The Damascus regime has repeatedly vowed to take back control of Idlib.
Assad's forces launched a blistering military campaign against the region in April, killing around 1,000 civilians and displacing more than 400,000 people from their homes.
A ceasefire announced by Moscow has largely held since late August.
But the Observatory says deadly bombardment and skirmishes have persisted, with more than 200 civilians killed in the region since the deal.
Syria's war has killed over 370,000 people and displaced millions from their homes since beginning in 2011 with the repression of protests.