Syrian government airstrikes have killed nearly 50 people in a rebel-held city this week.
The Britain-based Syrian Observatory for Human Rights said it counted 48 killed in two days of strikes on the city of Talbiseh.
The death toll is unusually high, even by the standards of the Syrian civil war.
Similar information was reported by a local Talbiseh activist group.
The Observatory said leading members of a rebel group were killed in the attacks on Monday and Tuesday, but did not identify which one. The bombings also crushed families under rubble, both groups reported.
State-run media said the army had targeted a meeting of "terrorists".
The victims included a mother and her five children, the Observatory said, adding that the death toll is likely to exceed 50 as residents are still pulling bodies from the rubble.
"Residents woke up from the massacre yesterday only to witness another terrifying massacre," said the local collective in a Facebook update, describing Talbiseh as a "destroyed" city "filled with civilians and displaced who cannot find bread to eat, chased by the shelling of regime forces".
Videos showed a man weeping as he clutched a lifeless baby, and residents praying over the shroud-wrapped bodies of a mother and her five children.
One rebel group, which identified itself as the Iman Bil-Lah faction, uploaded videos of its rebels operating in Talbiseh. The footage showed men firing mortars toward the nearby government-held city of Homs and heavy machine guns at Syrian aircraft. An unseen narrator on the video said the firing was in response to the airstrikes.
The group describes itself as part of the Free Syrian Army, a byword for a chaotic mix of more moderate rebel groups that seek Western support and arms.
The United Nations says more than 190,000 people have been killed since the 2011 start of Syria's conflict, which has transformed into a multi-layered civil war.