At least 12 people were killed when a Syrian army fighter jet crashed into a busy marketplace in the rebel-held northwestern town of Ariha on Monday, a monitor said.
Most of the dead were civilians on the ground in the town in Idlib province, which fell to a coalition of Islamist insurgents in May, according to the UK-based Observatory for Human Rights, which tracks violence across Syria.
Scores were also injured, it said. There was no immediate reaction from the Syrian army.
The military plane had been spotted earlier in a bombing raid in the area that has come under heavy aerial bombardment by the Syrian army in recent days, a rebel source said.
The fall of Ariha had left the insurgents in control of most of Idlib, a region that borders Turkey and neighbours President Bashar al-Assad's heartland in Latakia province on the Mediterranean coast.
The army has been trying to beat back insurgent gains that brought them closer to government-held coastal areas north of the capital Damascus.