The overnight military raid in Al-Tamanaa village killed a man and a 50-year-old woman, the head of the Britain-based Syrian Observatory for Human Rights, Rami Abdel Rahman, told AFP.
The northwestern Idlib province, which borders Turkey, is a stronghold of the Free Syrian Army and a hotbed of opposition to President Bashar al-Assad's regime.
Another civilian died by sniper fire in the central city of Homs, Abdel Rahman said, adding that he was gunned down at a security checkpoint in the neighbourhood of Qusayr.
Raids by security forces and clashes between regular troops and defectors saw 17 civilians, three rebels and five soldiers killed on Monday, when Syria held parliamentary elections that the opposition boycotted and Washington dismissed as "ludicrous."
Political analysts do not expect the election to lead to significant change in Syria, where a tenuous UN-backed ceasefire that came into effect on April 12 has failed to take hold.
More than 600 people have died since the truce began, according to the Observatory.
Voters cast their ballots in the capital and other regions, while in opposition strongholds residents boycotted the poll, instead staging protests and a general strike.
Several towns and villages across the country, including some neighbourhoods of Damascus, held demonstrations, boycotted the vote and organised a general strike amid reports of continued violence.
Shops were closed and streets empty in several areas of Hama, Idlib, northern Aleppo, Daraa in the south and Damascus itself, activists said.
According to the Observatory, more than 11,100 people have died in violence, most of them civilians, since an anti-regime uprising broke out in March last year.