A convoy carrying aid for some 40,000 people entered the besieged rebel-held Eastern Ghouta region outside Syria's capital Damascus on Monday, a United Nations spokeswoman said.
"We entered Eastern Ghouta... we are planning on delivering aid to Kafr Batna and Saqba (districts) today for 40,000" people, said Linda Tom, a spokeswoman for the UN's humanitarian coordination agency OCHA.
The joint UN-Syrian Arab Red Crescent convoy included 49 trucks carrying "eight thousand food parcels and a similar number of bags of flour, medicine, medical supplies, and other nutritional materials," Red Crescent spokeswoman Mona Kurdi said.
The delivery comes a week after residents and aid groups warned of a mounting hunger crisis in the region.
Doctors said they examine dozens of malnourished children a day and that at least two had died.
Eastern Ghouta was once a prime agricultural region.
But the rebel stronghold has been under a crushing government siege since 2013, causing shortages of food and medicine.
That has pushed up prices for whatever can be produced locally or smuggled in.
The region has been devastated by years of fighting, with government air strikes and shelling bringing down multi-storey buildings and rendering whole streets uninhabitable.
Basic services for the region's estimated 400,000 residents are virtually non-existent, with electricity produced only by generators and the available water often dirty and a vector for illness.
Aid has entered the area only sporadically, with the last delivery in September.
Convoys have generally only been able to deliver food and medical supplies that fall far short of the region's needs.