Low-level fighting also appeared to continue inside the city of Aleppo, 50 km (30 miles) from Idlib city, and there were heavier clashes around Aleppo, the British-based group said, as reported by Reuters.
The Syrian army announced the extension of a ceasefire in Aleppo late on Monday.
The airborne raids, by either Syrian or Russian warplanes, struck the town of Binnish, 6 km (4 miles) from the provincial capital Idlib. They wounded a number of others, the Observatory said.
Read alsoPentagon: IS leader in Iraq's Anbar killedIt said a local insurgent commander was among those killed. There were no immediate details about other casualties.
Idlib province, which borders Turkey, is almost completely controlled by insurgent groups, including the al Qaeda-affiliated Nusra Front and powerful Islamist group Ahrar al-Sham.
