BEIRUT -- The Syrian military unleashed heavy airstrikes and artillery bombardments targeting rebel strongholds in the north on Tuesday, killing at least 90 people, activists said.

The barrage came as the UN food agency warned that more Syrians are depending on assistance from the World Food Program to stay alive with the civil war worsening.

The airstrikes hit northern Idlib and Aleppo provinces, both bordering Turkey. Activists described them as some of the worst since rebels fighting to topple President Bashar Assad took over the key city of Maaret al-Numan in Idlib on Oct. 10. The city lies along the main highway connecting Aleppo with the cities to the south, including Homs and the capital Damascus.

Assad's regime has increasingly relied on warplanes in its struggle to crush rebels who have taken over large swathes of territory in the north.

Rami Abdul-Rahman, who heads the Britain-based activist group Syrian Observatory for Human Rights, said at least 90 people were killed in airstrikes and artillery shelling.

Fighting continued in Aleppo, Syria's largest city with 3 million residents and its former business capital. Airstrikes were reported in the town of al-Bab in Aleppo province.

In Geneva, World Food Program officials said some 1.4 million people required its assistance last month in many parts of Syria, adding that aid workers can't reach all those in need because of the raging conflict.

Also on Tuesday, Turkey allowed a Syria-bound cargo plane from Armenia to resume its journey after it landed in eastern Turkey for a search to make sure it carried humanitarian aid and not weapons.

Deputy Prime Minister Bulent Arinc said authorities had verified Armenia's statement that the plane carried relief supplies to Aleppo, the state-run Anatolia agency said.

The landing of the plane in the eastern city of Erzurum came a week after Turkey grounded and searched a Syrian plane that took off from Russia, and confiscated some of its cargo saying it contained military supplies destined for President Bashar al-Assad's government.

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