Syrian forces loyal to President Bashar al-Assad killed at least 15 people overnight in a Sunni Muslim village north-west of the city of Hama, activists said on Saturday.
The Syrian Observatory for Human Rights said a woman and two children were among those killed in the attack in the village of Sheikh Hadid by soldiers and pro-Assad militia.
The British-based group, which monitors violence in Syria through a network of activists and medical and security sources, said the killings followed attacks by rebels on military checkpoints in the area over the previous two days.
It said 26 people - 16 soldiers and 10 members of the pro-Assad National Defence Force - were killed when rebels attacked a nearby checkpoint on Thursday. There was also fighting in the village of Jalma, two miles (3 km) south of Sheikh Hadid, on Friday, it said.
The opposition Shaam News Network put the death toll in Sheikh Hadid in the dozens, but gave no details.
More than 100,000 people have been killed in Syria's civil war, which grew out of a 2011 uprising against President Bashar al-Assad. The conflict pits mainly Sunni Muslim rebels against a president whose Alawite faith is an offshoot of Shi'ite Islam.
The war has divided the Middle East along sectarian lines, with Shi'ite Iran and Shi'i'te fighters from Iraq as well as Lebanon's Hezbollah backing Assad. Sunni Muslim rulers in Turkey and the Gulf support the rebels, who have been joined by Sunni Islamist fighters from across the region.
The United States and Russia, who back opposing sides in the war, agreed one week ago on a timetable for dismantling Syria's chemical weapons arsenal after an attack in Damascus suburbs last month which killed hundreds of people.
But the accord has done nothing to stem the fighting with conventional weapons.
Rebels seized several villages south of Aleppo on Saturday as part of their efforts to cut Syria's biggest city off from Assad's forces and stop supplies and reinforcements from Damascus.
Internet video footage showed rebels from the Tawhid brigade firing a tank and a truck-mounted machine gun at army positions near the Sheikh Said suburb south of Aleppo.