Nine trucks carrying food and other supplies have crossed into Syria through a Turkish checkpoint.
They were the first to do so under a United Nations resolution authorising cross-border aid deliveries without Syrian government approval.
UN spokeswoman Amanda Pitt said the trucks contained desperately needed food, water purification tablets, and sanitation and shelter materials.
The UN humanitarian office has said that if security allows, aid could reach 2.9 million people through the four crossings.
So far more than 150,000 people have died in the three-year Syria conflict.