The Local Coordination Committees of Syria told CNN at least 25 people, including defected soldiers and one entire family, were killed in a "massacre committed by the regime forces in Idlib towns."
Activists said increased U.N. monitoring has stemmed the violence to some extent, but the government of President Bashar Assad is still out of compliance with a U.N.-brokered peace plan.
"Shelling has calmed, but this does not mean that the peace plan has been implemented," an activist in Homs identified only as Saleem told CNN. "Gunfire, rocket shelling, mortar shelling and arbitrary arrests still occur."
"Unfortunately, the monitors are like a guide for the Syrian regime: Wherever they go, usually people are killed after they leave," an activist identified as Ahmad said Monday.
Tuesday's slaughter followed car bomb blasts that killed at least 20 people Monday, the Syrian Observatory for Human Rights said.
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