The ambush is the second this week to target buses traveling between the regime-controlled areas and to be blamed on suspected Daesh militants.
Israel rarely confirms details of its operations in Syria, but says Iran's presence backing regime leader Bashar al Assad is a threat.
More than 20 air strikes targeted two mountains and three villages in the Jabal al Zawiya region and two other villages in the countryside of the Hama province, a war monitor and a civil defence group said.
The toll of nine dead could rise as some people were seriously injured in the raids, the Syrian Observatory for Human Rights reported.
Britain-based Syrian Observatory for Human Rights says heavily-bombarded Maarat al Numan "is nearly besieged," with residents of several villages scurrying for safety in the northwest of the country.
Idlib today bears the brunt of the Assad regime's Soleimani-inspired scorched earth strategy which will blight Syria for a long time to come.
A war monitor says "fierce clashes" between loyalist forces, militants and allied rebels were taking place one kilometre west of Khan Shaykhun in Idlib province.
The Syrian Observatory for Human Rights, a London-based war monitor, said that four children were among 15 civilians killed in air strikes by the Syrian regime and its ally Russia.
As the Syrian regime battles the last rebel stronghold, could it begin to release those detained in inhumane conditions since the beginning of the conflict?
"We will never withdraw from the zone," says Hayat Tahrir al Sham, the largest militant group in northwestern Idlib, two days after regime announced a truce between it and opposition forces.
The war in Syria, now in its eighth year, has seen children paying the heaviest price. At least 33 have been killed since June this year, compared to 31 children during the entirety of 2018.
Opposition factions seized Hamameyat village and a hilltop in Hama province amid deadly clashes, war monitor SOHR says.
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