At least 21 people, including at least three children, were killed on December 4 in a series of air strikes on the northwestern Syrian province of Idlib, a monitoring group and activists said.
The Syrian Observatory for Human Rights said dozens more were wounded in the air strikes that hit the village of Kafranbel. It said the bombings appeared to have been carried out by a Russian warplane.
The AFP news agency quoted eyewitness Hossam Hosber as saying "six strikes hit houses and a crowded local market."
Idlib is mostly held by a rebel coalition that includes the extremist group Jabhat Fateh al-Sham, formerly known as the Al-Nusra Front, Al-Qaeda's Syrian affiliate.
The air strikes come amid an ongoing government offensive in a rebel-held area in the northern city of Aleppo.
A spokesman for the Syrian military told the Associated Press that the army is offering rebel fighters in besieged eastern Aleppo an opportunity to leave the area.
Samir Suleiman was quoted by the news agency as saying that those who choose to stay will face "inevitable death."
Suleiman said government forces and allied militias have retaken more than 50 percent of neighborhoods in eastern Aleppo.
"We will continue fighting until we restore stability and security to all neighborhoods" of Aleppo, including its historic quarters known as Old Aleppo, Suleiman said.
Eastern Aleppo has been under government siege since July, facing severe shortages of food, fuel, and medical supplies.
Based on reporting by dpa, AFP, and AP