Shopkeepers and residents in Syria's Idlib city have found relief from airstrikes but remain wary after a cease-fire halted fierce government bombing against the rebel foothold.

For three months, an army offensive backed by Russia has killed at least 400 people in northwest Syria and uprooted more than 440,000, the United Nations says.

Since Damascus declared a cease-fire on Thursday night, its warplanes have not mounted airstrikes, though the combatants are still shelling each other.