Nearly three weeks after a Saudi-led coalition blockaded Yemen’s airports and seaports, cutting off much of the country from desperately needed aid, shipments have begun re-entering ports held by Houthi rebels.

The blockade had left millions of people without reliable access to medicine and exacerbated a food crisis that has left much of the country teetering on the brink of famine.

On Sunday, the key seaport of Al Hudaydah received a shipment of flour, Reuters reported, and a day earlier aid planes were allowed to land at the main airport in Sana, the capital.

Humanitarian groups have warned that the arrival of lifesaving supplies should not be misinterpreted as an end to the pressing crisis, but instead as the first step in re-establishing a consistent flow of food and medicine to a country with millions of civilians in need.